[Docs] [txt|pdf] [Tracker] [WG] [Email] [Diff1] [Diff2] [Nits] [IPR]

Versions: (draft-sajassi-l2vpn-evpn-inter-subnet-forwarding) 00 01 02 03 04 05 06 07 08 09

BESS WorkGroup                                                A. Sajassi
Internet-Draft                                                  S. Salam
Intended status: Standards Track                               S. Thoria
Expires: December 16, 2020                                 Cisco Systems
                                                                J. Drake
                                                                 Juniper
                                                              J. Rabadan
                                                                   Nokia
                                                           June 14, 2020


                Integrated Routing and Bridging in EVPN
            draft-ietf-bess-evpn-inter-subnet-forwarding-09

Abstract

   EVPN provides an extensible and flexible multi-homing VPN solution
   over an MPLS/IP network for intra-subnet connectivity among Tenant
   Systems and End Devices that can be physical or virtual.  However,
   there are scenarios for which there is a need for a dynamic and
   efficient inter-subnet connectivity among these Tenant Systems and
   End Devices while maintaining the multi-homing capabilities of EVPN.
   This document describes an Integrated Routing and Bridging (IRB)
   solution based on EVPN to address such requirements.

Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119] and
   RFC 8174 [RFC8174].

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on December 16, 2020.



Sajassi, et al.         Expires December 16, 2020               [Page 1]


Internet-Draft   Integrated Routing and Bridging in EVPN       June 2020


Copyright Notice

   Copyright (c) 2020 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   5
   3.  EVPN PE Model for IRB Operation . . . . . . . . . . . . . . .   6
   4.  Symmetric and Asymmetric IRB  . . . . . . . . . . . . . . . .   7
     4.1.  IRB Interface and its MAC and IP addresses  . . . . . . .  10
   5.  Symmetric IRB Procedures  . . . . . . . . . . . . . . . . . .  12
     5.1.  Control Plane - Advertising PE  . . . . . . . . . . . . .  12
     5.2.  Control Plane - Receiving PE  . . . . . . . . . . . . . .  13
     5.3.  Subnet route advertisement  . . . . . . . . . . . . . . .  14
     5.4.  Data Plane - Ingress PE . . . . . . . . . . . . . . . . .  14
     5.5.  Data Plane - Egress PE  . . . . . . . . . . . . . . . . .  15
   6.  Asymmetric IRB Procedures . . . . . . . . . . . . . . . . . .  16
     6.1.  Control Plane - Advertising PE  . . . . . . . . . . . . .  16
     6.2.  Control Plane - Receiving PE  . . . . . . . . . . . . . .  16
     6.3.  Data Plane - Ingress PE . . . . . . . . . . . . . . . . .  18
     6.4.  Data Plane - Egress PE  . . . . . . . . . . . . . . . . .  18
   7.  Mobility Procedure  . . . . . . . . . . . . . . . . . . . . .  19
     7.1.  Initiating an ARP Request upon a Move . . . . . . . . . .  19
     7.2.  Sending Data Traffic without an ARP Request . . . . . . .  20
     7.3.  Silent Host . . . . . . . . . . . . . . . . . . . . . . .  22
   8.  BGP Encoding  . . . . . . . . . . . . . . . . . . . . . . . .  23
     8.1.  Router's MAC Extended Community . . . . . . . . . . . . .  23
   9.  Operational Models for Symmetric Inter-Subnet Forwarding  . .  24
     9.1.  IRB forwarding on NVEs for Tenant Systems . . . . . . . .  24
       9.1.1.  Control Plane Operation . . . . . . . . . . . . . . .  25
       9.1.2.  Data Plane Operation  . . . . . . . . . . . . . . . .  26
     9.2.  IRB forwarding on NVEs for Subnets behind Tenant Systems   28
       9.2.1.  Control Plane Operation . . . . . . . . . . . . . . .  29
       9.2.2.  Data Plane Operation  . . . . . . . . . . . . . . . .  30
   10. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  31
   11. Security Considerations . . . . . . . . . . . . . . . . . . .  31



Sajassi, et al.         Expires December 16, 2020               [Page 2]


Internet-Draft   Integrated Routing and Bridging in EVPN       June 2020


   12. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  32
   13. Intellectual Property Considerations  . . . . . . . . . . . .  32
   14. References  . . . . . . . . . . . . . . . . . . . . . . . . .  32
     14.1.  Normative References . . . . . . . . . . . . . . . . . .  32
     14.2.  Informative References . . . . . . . . . . . . . . . . .  32
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  33

1.  Terminology

   AC: Attachment Circuit

   ARP: Address Resolution Protocol

   BD: Broadcast Domain.  As per [RFC7432], an EVI consists of a single
   or multiple BDs.  In case of VLAN-bundle and VLAN-based service
   models (see [RFC7432]), a BD is equivalent to an EVI.  In case of
   VLAN-aware bundle service model, an EVI contains multiple BDs.  Also,
   in this document, BD and subnet are equivalent terms.

   BD Route Target: refers to the Broadcast Domain assigned Route Target
   [RFC4364].  In case of VLAN-aware bundle service model, all the BD
   instances in the MAC-VRF share the same Route Target

   BT: Bridge Table.  The instantiation of a BD in a MAC-VRF, as per
   [RFC7432].

   DGW: Data Center Gateway

   Ethernet A-D route: Ethernet Auto-Discovery (A-D) route, as per
   [RFC7432].

   Ethernet NVO tunnel: refers to Network Virtualization Overlay tunnels
   with Ethernet payload.  Examples of this type of tunnels are VXLAN or
   GENEVE.

   EVI: EVPN Instance spanning the NVE/PE devices that are participating
   on that EVPN, as per [RFC7432].

   EVPN: Ethernet Virtual Private Networks, as per [RFC7432].

   GRE: Generic Routing Encapsulation

   GW IP: Gateway IP Address

   IPL: IP Prefix Length

   IP NVO tunnel: it refers to Network Virtualization Overlay tunnels
   with IP payload (no MAC header in the payload).



Sajassi, et al.         Expires December 16, 2020               [Page 3]


Internet-Draft   Integrated Routing and Bridging in EVPN       June 2020


   IP-VRF: A VPN Routing and Forwarding table for IP routes on an NVE/
   PE.  The IP routes could be populated by EVPN and IP-VPN address
   families.  An IP-VRF is also an instantiation of a layer 3 VPN in an
   NVE/PE.

   IRB: Integrated Routing and Bridging interface.  It connects an IP-
   VRF to a BD (or subnet).

   MAC-VRF: A Virtual Routing and Forwarding table for Media Access
   Control (MAC) addresses on an NVE/PE, as per [RFC7432].  A MAC-VRF is
   also an instantiation of an EVI in an NVE/PE.

   ML: MAC address length

   ND: Neighbor Discovery Protocol

   NVE: Network Virtualization Edge

   GENEVE: Generic Network Virtualization Encapsulation, [GENEVE]

   NVO: Network Virtualization Overlays

   RT-2: EVPN route type 2, i.e., MAC/IP Advertisement route, as defined
   in [RFC7432]

   RT-5: EVPN route type 5, i.e., IP Prefix route.  As defined in
   Section 3 of [EVPN-PREFIX]

   SN: Subnet

   TS: Tenant System

   VA: Virtual Appliance

   VNI: Virtual Network Identifier.  As in [RFC8365], the term is used
   as a representation of a 24-bit NVO instance identifier, with the
   understanding that VNI will refer to a VXLAN Network Identifier in
   VXLAN, or Virtual Network Identifier in GENEVE, etc. unless it is
   stated otherwise.

   VTEP: VXLAN Termination End Point, as in [RFC7348].

   VXLAN: Virtual Extensible LAN, as in [RFC7348].

   This document also assumes familiarity with the terminology of
   [RFC7432], [RFC8365] and [RFC7365].





Sajassi, et al.         Expires December 16, 2020               [Page 4]


Internet-Draft   Integrated Routing and Bridging in EVPN       June 2020


2.  Introduction

   EVPN [RFC7432] provides an extensible and flexible multi-homing VPN
   solution over an MPLS/IP network for intra-subnet connectivity among
   Tenant Systems (TSes) and End Devices that can be physical or
   virtual; where an IP subnet is represented by an EVI for a VLAN-based
   service or by an (EVI, VLAN) for a VLAN-aware bundle service.
   However, there are scenarios for which there is a need for a dynamic
   and efficient inter-subnet connectivity among these Tenant Systems
   and End Devices while maintaining the multi-homing capabilities of
   EVPN.  This document describes an Integrated Routing and Bridging
   (IRB) solution based on EVPN to address such requirements.

   The inter-subnet communication is traditionally achieved at
   centralized L3 Gateway (L3GW) devices where all the inter-subnet
   forwarding are performed and all the inter-subnet communication
   policies are enforced.  When two TSes belonging to two different
   subnets connected to the same PE, wanted to communicate with each
   other, their traffic needed to be back hauled from the PE all the way
   to the centralized gateway where inter-subnet switching is performed
   and then back to the PE.  For today's large multi-tenant data center,
   this scheme is very inefficient and sometimes impractical.

   In order to overcome the drawback of centralized layer-3 GW approach,
   IRB functionality is needed on the PEs (also referred to as EVPN
   NVEs) attached to TSes in order to avoid inefficient forwarding of
   tenant traffic (i.e., avoid back-hauling and hair-pinning).  When a
   PE with IRB capability receives tenant traffic over an Attachment
   Circuit (AC), it can not only locally bridge the tenant intra-subnet
   traffic but also can locally route the tenant inter-subnet traffic on
   a packet by packet basis thus meeting the requirements for both intra
   and inter-subnet forwarding and avoiding non-optimum traffic
   forwarding associated with centralized layer-3 GW approach.

   Some TSes run non-IP protocols in conjunction with their IP traffic.
   Therefore, it is important to handle both kinds of traffic optimally
   - e.g., to bridge non-IP and intra-subnet traffic and to route inter-
   subnet IP traffic.  Therefore, the solution needs to meet the
   following requirements:

   R1: The solution MUST allow for both inter-subnet and intra-subnet
   traffic belonging to the same tenant to be locally routed and bridged
   respectively.  The solution MUST provide IP routing for inter-subnet
   traffic and Ethernet Bridging for intra-subnet traffic.

   R2: The solution MUST support bridging for non-IP traffic.





Sajassi, et al.         Expires December 16, 2020               [Page 5]


Internet-Draft   Integrated Routing and Bridging in EVPN       June 2020


   R3: The solution MUST allow inter-subnet switching to be disabled on
   a per VLAN basis on PEs where the traffic needs to be back hauled to
   another node (i.e., for performing FW or DPI functionality).

3.  EVPN PE Model for IRB Operation

   Since this document discusses IRB operation in relationship to EVPN
   MAC-VRF, IP-VRF, EVI, Bridge Domain (BD), Bridge Table (BT), and IRB
   interfaces, it is important to understand the relationship among
   these components.  Therefore, the following PE model is illustrated
   below to a) describe these components and b) illustrate the
   relationship among them.


      +-------------------------------------------------------------+
      |                                                             |
      |              +------------------+                    IRB PE |
      | Attachment   | +------------------+                         |
      | Circuit(AC1) | |  +----------+    |                MPLS/NVO tnl
    ----------------------*Bridge    |    |                    +-----
      |              | |  |Table(BT1)|    |    +-----------+  / \    \
      |              | |  |          *---------*           |<--> |Eth|
      |              | |  |  VLAN x  |    |IRB1|           |  \ /    /
      |              | |  +----------+    |    |           |   +-----
      |              | |     ...          |    |  IP-VRF1  |        |
      |              | |  +----------+    |    |  RD2/RT2  |MPLS/NVO tnl
      |              | |  |Bridge    |    |    |           |   +-----
      |              | |  |Table(BT2)|    |IRB2|           |  / \    \
      |              | |  |          *---------*           |<--> |IP |
    ----------------------*  VLAN y  |    |    +-----------+  \ /    /
      |  AC2         | |  +----------+    |                    +-----
      |              | |    MAC-VRF1      |                         |
      |              +-+    RD1/RT1       |                         |
      |                +------------------+                         |
      |                                                             |
      |                                                             |
      +-------------------------------------------------------------+

                      Figure 1: EVPN IRB PE Model


   A tenant needing IRB services on a PE, requires an IP Virtual Routing
   and Forwarding table (IP-VRF) along with one or more MAC Virtual
   Routing and Forwarding tables (MAC-VRFs).  An IP-VRF, as defined in
   [RFC4364], is the instantiation of an IPVPN instance in a PE.  A MAC-
   VRF, as defined in [RFC7432], is the instantiation of an EVI (EVPN
   Instance) in a PE.  A MAC-VRF can consists of one or more Bridge
   Tables (BTs) where each BT corresponds to a VLAN (broadcast domain -



Sajassi, et al.         Expires December 16, 2020               [Page 6]


Internet-Draft   Integrated Routing and Bridging in EVPN       June 2020


   BD).  If service interfaces for an EVPN PE are configured in VLAN-
   Based mode (i.e., section 6.1 of RFC7432), then there is only a
   single BT per MAC-VRF (per EVI) - i.e., there is only one tenant VLAN
   per EVI.  However, if service interfaces for an EVPN PE are
   configured in VLAN-Aware Bundle mode (i.e., section 6.3 of RFC7432),
   then there are several BTs per MAC-VRF (per EVI) - i.e., there are
   several tenant VLANs per EVI.

   Each BT is connected to a IP-VRF via a L3 interface called IRB
   interface.  Since a single tenant subnet is typically (and in this
   document) represented by a VLAN (and thus supported by a single BT),
   for a given tenant there are as many BTs as there are subnets and
   thus there are also as many IRB interfaces between the tenant IP-VRF
   and the associated BTs as shown in the PE model above.

   IP-VRF is identified by its corresponding route target and route
   distinguisher and MAC-VRF is also identified by its corresponding
   route target and route distinguisher.  If operating in EVPN VLAN-
   Based mode, then a receiving PE that receives an EVPN route with MAC-
   VRF route target can identify the corresponding BT; however, if
   operating in EVPN VLAN-Aware Bundle mode, then the receiving PE needs
   both the MAC-VRF route target and VLAN ID in order to identify the
   corresponding BT.

4.  Symmetric and Asymmetric IRB

   This document defines and describes two types of IRB solutions -
   namely symmetric and asymmetric IRB.  The description of symmetric
   and asymmetric IRB procedures relating to data path operations and
   tables in this document is a logical view of data path lookups and
   related tables.  Actual implementations, while following this logical
   view, may not strictly adhere to it for performance tradeoffs.
   Specifically,

   o  references to ARP table in the context of asymmetric IRB is a
      logical view of a forwarding table that maintains an IP to MAC
      binding entry on a layer 3 interface for both IPv4 and IPv6.
      These entries are not subject to ARP or ND protocol.  For IP to
      MAC bindings learnt via EVPN, an implementation may choose to
      import these bindings directly to the respective forwarding table
      (such as an adjacency/next-hop table) as opposed to importing them
      to ARP or ND protocol tables.

   o  references to host IP lookup followed by a host MAC lookup in the
      context of asymmetric IRB MAY be collapsed into a single IP lookup
      in a hardware implementation.





Sajassi, et al.         Expires December 16, 2020               [Page 7]


Internet-Draft   Integrated Routing and Bridging in EVPN       June 2020


   In symmetric IRB as its name implies, the lookup operation is
   symmetric at both ingress and egress PEs - i.e., both ingress and
   egress PEs perform lookups on both MAC and IP addresses.  The ingress
   PE performs a MAC lookup followed by an IP lookup and the egress PE
   performs a IP lookup followed by a MAC lookup as depicted in the
   following figure.



                  Ingress PE                   Egress PE
            +-------------------+        +------------------+
            |                   |        |                  |
            |    +-> IP-VRF ----|---->---|-----> IP-VRF -+  |
            |    |              |        |               |  |
            |   BT1        BT2  |        |  BT3         BT2 |
            |    |              |        |               |  |
            |    ^              |        |               v  |
            |    |              |        |               |  |
            +-------------------+        +------------------+
                 ^                                       |
                 |                                       |
           TS1->-+                                       +->-TS2
                           Figure 2: Symmetric IRB


   In symmetric IRB as shown in figure-2, the inter-subnet forwarding
   between two PEs is done between their associated IP-VRFs.  Therefore,
   the tunnel connecting these IP-VRFs can be either IP-only tunnel (in
   case of MPLS or GENEVE encapsulation) or Ethernet NVO tunnel (in case
   of VxLAN encapsulation).  If it is an Ethernet NVO tunnel, the TS1's
   IP packet is encapsulated in an Ethernet header consisting of ingress
   and egress PEs MAC addresses - i.e., there is no need for ingress PE
   to use the destination TS2's MAC address.  Therefore, in symmetric
   IRB, there is no need for the ingress PE to maintain ARP entries for
   destination TS2's IP and MAC addresses association in its ARP table.
   Each PE participating in symmetric IRB only maintains ARP entries for
   locally connected hosts and maintains MAC-VRFs/BTs for only locally
   configured subnets.

   In asymmetric IRB, the lookup operation is asymmetric and the ingress
   PE performs three lookups; whereas the egress PE performs a single
   lookup - i.e., the ingress PE performs a MAC lookup, followed by an
   IP lookup, followed by a MAC lookup again; whereas, the egress PE
   performs just a single MAC lookup as depicted in figure 3 below.







Sajassi, et al.         Expires December 16, 2020               [Page 8]


Internet-Draft   Integrated Routing and Bridging in EVPN       June 2020


               Ingress PE                       Egress PE
            +-------------------+        +------------------+
            |                   |        |                  |
            |    +-> IP-VRF ->  |        |      IP-VRF      |
            |    |           |  |        |                  |
            |   BT1        BT2  |        |  BT3         BT2 |
            |    |           |  |        |              | | |
            |    |           +--|--->----|--------------+ | |
            |    |              |        |                v |
            +-------------------+        +----------------|-+
                 ^                                        |
                 |                                        |
           TS1->-+                                        +->-TS2
                           Figure 3: Asymmetric IRB


   In asymmetric IRB as shown in figure-3, the inter-subnet forwarding
   between two PEs is done between their associated MAC-VRFs/BTs.
   Therefore, the MPLS or NVO tunnel used for inter-subnet forwarding
   MUST be of type Ethernet.  Since only MAC lookup is performed at the
   egress PE (e.g., no IP lookup), the TS1's IP packets need to be
   encapsulated with the destination TS2's MAC address.  In order for
   ingress PE to perform such encapsulation, it needs to maintain TS2's
   IP and MAC address association in its ARP table.  Furthermore, it
   needs to maintain destination TS2's MAC address in the corresponding
   BT even though it may not have any TSes of the corresponding subnet
   locally attached.  In other words, each PE participating in
   asymmetric IRB MUST maintain ARP entries for remote hosts (hosts
   connected to other PEs) as well as maintain MAC-VRFs/BTs and IRB
   interfaces for ALL subnets in an IP VRF including subnets that may
   not be locally attached.

   The following subsection defines the control and data planes
   procedures for symmetric and asymmetric IRB on ingress and egress
   PEs.  The following figure is used in description of these procedures
   where it shows a single IP-VRF and a number of BTs on each PE for a
   given tenant.  The IP-VRF of the tenant (i.e., IP-VRF1) is connected
   to each BT via its associated IRB interface.  Each BT on a PE is
   associated with a unique VLAN (e.g., with a BD) where in turn is
   associated with a single MAC-VRF in case of VLAN-Based mode or a
   number of BTs can be associated with a single MAC-VRF in case of
   VLAN-Aware Bundle mode.  Whether the service interface on a PE is
   VLAN-Based or VLAN-Aware Bundle mode does not impact the IRB
   operation and procedures.  It mainly impacts the setting of Ethernet
   tag field in EVPN BGP routes as described in [RFC7432].






Sajassi, et al.         Expires December 16, 2020               [Page 9]


Internet-Draft   Integrated Routing and Bridging in EVPN       June 2020


                    PE 1         +---------+
              +-------------+    |         |
      TS1-----|         MACx|    |         |        PE2
    (IP1/M1)  |(BT1)        |    |         |   +-------------+
      TS5-----|      \      |    |  MPLS/  |   |MACy  (BT3)  |-----TS3
    (IP5/M5)  |Mx/IPx \     |    |  VxLAN/ |   |     /       | (IP3/M3)
              |    (IP-VRF1)|----|  NVGRE  |---|(IP-VRF1)    |
              |       /     |    |         |   |     \       |
      TS2-----|(BT2) /      |    |         |   |      (BT1)  |-----TS4
    (IP2/M2)  |             |    |         |   |             |  (IP4/M4)
              +-------------+    |         |   +-------------+
                                 |         |
                                 +---------+

                       Figure 4: IRB forwarding


4.1.  IRB Interface and its MAC and IP addresses

   To support inter-subnet forwarding on a PE, the PE acts as an IP
   Default Gateway from the perspective of the attached Tenant Systems
   where default gateway MAC and IP addresses are configured on each IRB
   interface associated with its subnet and falls into one of the
   following two options:

   1.  All the PEs for a given tenant subnet use the same anycast
       default gateway IP and MAC addresses.  On each PE, this default
       gateway IP and MAC addresses correspond to the IRB interface
       connecting the BT associated with the tenant's VLAN to the
       corresponding tenant's IP-VRF.

   2.  Each PE for a given tenant subnet uses the same anycast default
       gateway IP address but its own MAC address.  These MAC addresses
       are aliased to the same anycast default gateway IP address
       through the use of the Default Gateway extended community as
       specified in [RFC7432], which is carried in the EVPN MAC/IP
       Advertisement routes.  On each PE, this default gateway IP
       address along with its associated MAC addresses correspond to the
       IRB interface connecting the BT associated with the tenant's VLAN
       to the corresponding tenant's IP-VRF.

   It is worth noting that if the applications that are running on the
   TSes are employing or relying on any form of MAC security, then
   either the first model (i.e. using anycast MAC address) should be
   used to ensure that the applications receive traffic from the same
   IRB interface MAC address that they are sending to, or if the second
   model is used, then the IRB interface MAC address MUST be the one




Sajassi, et al.         Expires December 16, 2020              [Page 10]


Internet-Draft   Integrated Routing and Bridging in EVPN       June 2020


   used in the initial ARP reply or ND Neighbor Advertisement (NA)for
   that TS.

   Although both of these options are equally applicable to both
   symmetric and asymmetric IRB, the option-1 is recommended because of
   the ease of anycast MAC address provisioning on not only the IRB
   interface associated with a given subnet across all the PEs
   corresponding to that VLAN but also on all IRB interfaces associated
   with all the tenant's subnets across all the PEs corresponding to all
   the VLANs for that tenant.  Furthermore, it simplifies the operation
   as there is no need for Default Gateway extended community
   advertisement and its associated MAC aliasing procedure.  Yet another
   advantage is that following host mobility, the host does not need to
   refresh the default GW ARP/ND entry.

   If option-1 is used, an implementation MAY choose to auto-derive the
   anycast MAC address.  If auto-derivation is used, the anycast MAC
   MUST be auto-derived out of the following ranges (which are defined
   in [RFC5798]):

   o  Anycast IPv4 IRB case: 00-00-5E-00-01-{VRID} (in hex, in Internet
      standard bit-order)

   o  Anycast IPv6 IRB case: 00-00-5E-00-02-{VRID} (in hex, in Internet
      standard bit-order)

   Where the last octet is generated based on a configurable Virtual
   Router ID (VRID, range 1-255)).  If not explicitly configured, the
   default value for the VRID octet is '01'.  Auto-derivation of the
   anycast MAC can only be used if there is certainty that the auto-
   derived MAC does not collide with any customer MAC address.

   In addition to IP anycast addresses, IRB interfaces can be configured
   with non-anycast IP addresses for the purpose of OAM (such as
   traceroute/ping to these interfaces) for both symmetric and
   asymmetric IRB.  These IP addresses need to be distributed as VPN
   routes when PEs operate in symmetric IRB mode.  However, they don't
   need to be distributed if the PEs are operating in asymmetric IRB
   mode and the non-anycast IP addresses are configured along with
   individual MACs.

   Irrespective of using only the anycast address or both anycast and
   non-anycast addresses on the same IRB, when a TS sends an ARP request
   or ND Neighbor Solicitation (NS) to the PE that is attached to, the
   request is sent for the anycast IP address of the IRB interface
   associated with the TS's subnet and the reply will use anycast MAC
   address (in both Source MAC in the Ethernet header and Sender
   hardware address in the payload).  For example, in figure 4, TS1 is



Sajassi, et al.         Expires December 16, 2020              [Page 11]


Internet-Draft   Integrated Routing and Bridging in EVPN       June 2020


   configured with the anycast IPx address as its default gateway IP
   address and thus when it sends an ARP request for IPx (anycast IP
   address of the IRB interface for BT1), the PE1 sends an ARP reply
   with the MACx which is the anycast MAC address of that IRB interface.
   Traffic routed from IP-VRF1 to TS1 SHOULD use the anycast MAC address
   as source MAC address.

5.  Symmetric IRB Procedures

5.1.  Control Plane - Advertising PE

   When a PE (e.g., PE1 in figure 4 above) learns MAC and IP address of
   a TS (via an ARP request), it adds the MAC address to the
   corresponding MAC-VRF/BT of that tenant's subnet and adds the IP
   address to the IP-VRF for that tenant.  Furthermore, it adds this
   TS's MAC and IP address association to its ARP table.  It then builds
   an EVPN MAC/IP Advertisement route (type 2) as follows and advertises
   it to other PEs participating in that tenant's VPN.

   o  The Length field of the BGP EVPN NLRI for an EVPN MAC/IP
      Advertisement route MUST be either 40 (if IPv4 address is carried)
      or 52 (if IPv6 address is carried).

   o  Route Distinguisher (RD), Ethernet Segment Identifier, Ethernet
      Tag ID, MAC Address Length, MAC Address, IP Address Length, IP
      Address, and MPLS Label1 fields MUST be set per [RFC7432] and
      [RFC8365].

   o  The MPLS Label2 field is set to either an MPLS label or a VNI
      corresponding to the tenant's IP-VRF.  In case of an MPLS label,
      this field is encoded as 3 octets, where the high-order 20 bits
      contain the label value.

   Just as in [RFC7432], the RD, Ethernet Tag ID, MAC Address Length,
   MAC Address, IP Address Length, and IP Address fields are part of the
   route key used by BGP to compare routes.  The rest of the fields are
   not part of the route key.

   This route is advertised along with the following two extended
   communities:

   1.  Tunnel Type Extended Community

   2.  Router's MAC Extended Community

   For symmetric IRB mode, Router's MAC EC is needed to carry the PE's
   overlay MAC address (e.g., inner MAC address in NVO encapsulation)
   which is used for IP-VRF to IP-VRF communications with Ethernet NVO



Sajassi, et al.         Expires December 16, 2020              [Page 12]


Internet-Draft   Integrated Routing and Bridging in EVPN       June 2020


   tunnel.  If MPLS or IP-only NVO tunnel is used, then there is no need
   to send Router's MAC Extended Community along with this route.

   This route MUST be advertised with two route targets - one
   corresponding to the MAC-VRF of the tenant's subnet and another
   corresponding to the tenant's IP-VRF.

5.2.  Control Plane - Receiving PE

   When a PE (e.g., PE2 in figure 4 above) receives this EVPN MAC/IP
   Advertisement route, it performs the following:

   o  Using MAC-VRF Route Target (and Ethernet Tag if different from
      zero), it identifies the corresponding MAC-VRF (and BT).  If the
      MAC- VRF (and BT) exists (e.g., it is locally configured) then it
      imports the MAC address into it.  Otherwise, it does not import
      the MAC address.

   o  Using IP-VRF route target, it identifies the corresponding IP-VRF
      and imports the IP address into it.

   The inclusion of MPLS label2 field in this route signals to the
   receiving PE that this route is for symmetric IRB mode and MPLS
   label2 needs to be installed in forwarding path to identify the
   corresponding IP-VRF.

   If the receiving PE receives this route with both the MAC-VRF and IP-
   VRF route targets but the MAC/IP Advertisement route does not include
   MPLS label2 field and if the receiving PE supports asymmetric IRB
   mode, then the receiving PE installs the MAC address in the
   corresponding MAC-VRF and (IP, MAC) association in the ARP table for
   that tenant (identified by the corresponding IP-VRF route target).

   If the receiving PE receives this route with both the MAC-VRF and IP-
   VRF route targets and if the receiving PE does not support either
   asymmetric or symmetric IRB modes, then if it has the corresponding
   MAC-VRF, it only imports the MAC address; otherwise, if it doesn't
   have the corresponding MAC-VRF, it MUST not import this route.

   If the receiving PE receives this route with both the MAC-VRF and IP-
   VRF route targets and the MAC/IP Advertisement route includes MPLS
   label2 field but the receiving PE only supports asymmetric IRB mode,
   then the receiving PE MUST ignore MPLS label2 field and install the
   MAC address in the corresponding MAC-VRF and (IP, MAC) association in
   the ARP table for that tenant (identified by the corresponding IP-VRF
   route target).





Sajassi, et al.         Expires December 16, 2020              [Page 13]


Internet-Draft   Integrated Routing and Bridging in EVPN       June 2020


5.3.  Subnet route advertisement

   In case of symmetric IRB, a layer-3 subnet and IRB interface
   corresponding to a MAC-VRF/BT is required to be provisioned at a PE
   only if that PE has locally attached hosts in that subnet.  In order
   to enable inter-subnet routing across PEs in a deployment where all
   subnets are not provisioned at all PEs participating in an EVPN IRB
   instance, PEs MUST advertise local subnet routes as RT-5.  These
   subnet routes are required for bootstrapping host (MAC,IP) learning
   using gleaning procedures initiated by an inter-subnet data packet.

   Consider a subnet A that is locally attached to PE1 and subnet B that
   is locally attached to PE2 and to PE3.  Host A in subnet A, that is
   attached to PE1 initiates a data packet destined to host B in subnet
   B that is attached to PE3.  If host B's (MAC, IP) has not yet been
   learnt either via a gratuitous ARP OR via a prior gleaning procedure,
   a new gleaning procedure MUST be triggered for host B's (MAC, IP) to
   be learnt and advertised across the EVPN network.  Since host B's
   subnet is not local to PE1, an IP lookup for host B at PE1 will not
   trigger this gleaning procedure for host B's (MAC, IP).  Therefore,
   PE1 MUST learn subnet B's prefix route via RT-5 advertised from PE2
   and PE3, so it can route the packet to one of the PEs that have
   subnet B locally attached.  Once the packet is received at PE2 OR
   PE3, and the route lookup yields a glean result, an ARP request is
   triggered and flooded across the layer-2 overlay.  This ARP request
   would be received and replied to by host B, resulting in host B (MAC,
   IP) learning at PE3, and its advertisement across the EVPN network.
   Packets from host A to host B can now be routed directly from PE1 to
   PE3.  Advertisement of local subnet RT-5 for an IP VRF MAY typically
   be achieved via provisioning connected route redistribution to BGP.

5.4.  Data Plane - Ingress PE

   When an Ethernet frame is received by an ingress PE (e.g., PE1 in
   figure 4 above), the PE uses the AC ID (e.g., VLAN ID) to identify
   the associated MAC-VRF/BT and it performs a lookup on the destination
   MAC address.  If the MAC address corresponds to its IRB Interface MAC
   address, the ingress PE deduces that the packet must be inter-subnet
   routed.  Hence, the ingress PE performs an IP lookup in the
   associated IP-VRF table.  The lookup identifies BGP next hop of
   egress PE along with the tunnel/encapsulation type and the associated
   MPLS/VNI values.

   If the tunnel type is that of MPLS or IP-only NVO tunnel, then TS's
   IP packet is sent over the tunnel without any Ethernet header.
   However, if the tunnel type is that of Ethernet NVO tunnel, then an
   Ethernet header needs to be added to the TS's IP packet.  The source
   MAC address of this inner Ethernet header is set to the ingress PE's



Sajassi, et al.         Expires December 16, 2020              [Page 14]


Internet-Draft   Integrated Routing and Bridging in EVPN       June 2020


   router MAC address and the destination MAC address of this inner
   Ethernet header is set to the egress PE's router MAC address learnt
   via Router's MAC extended community attached to the route.  MPLS VPN
   label is set to the received label2 in the route.  In case of
   Ethernet NVO tunnel type, VNI may be set one of two ways:

   o  downstream mode: VNI is set to the received label2 in the route
      which is downstream assigned.

   o  global mode: VNI is set to the received label2 in the route which
      is domain-wide assigned.  This VNI value from received label2 MUST
      be the same as the locally configured VNI for the IP VRF as all
      PEs in the NVO MUST be configured with the same IP VRF VNI for
      this mode of operation.

   PE's may be configured to operate in one of these two modes depending
   on the administrative domain boundaries across PEs participating in
   the NVO, and PE's capability to support downstream VNI mode.

   In case of NVO tunnel encapsulation, the outer source and destination
   IP addresses are set to the ingress and egress PE BGP next-hop IP
   addresses respectively.

5.5.  Data Plane - Egress PE

   When the tenant's MPLS or NVO encapsulated packet is received over an
   MPLS or NVO tunnel by the egress PE, the egress PE removes NVO tunnel
   encapsulation and uses the VPN MPLS label (for MPLS encapsulation) or
   VNI (for NVO encapsulation) to identify the IP-VRF in which IP lookup
   needs to be performed.  If the VPN MPLS label or VNI identifies a
   MAC- VRF instead of an IP-VRF, then the procedures in section 6.4 for
   asymmetric IRB are executed.

   The lookup in the IP-VRF identifies a local adjacency to the IRB
   interface associated with the egress subnet's MAC-VRF/BT.

   The egress PE gets the destination TS's MAC address for that TS's IP
   address from its ARP table, it encapsulates the packet with that
   destination MAC address and a source MAC address corresponding to
   that IRB interface and sends the packet to its destination subnet
   MAC-VRF/BT.

   The destination MAC address lookup in the MAC-VRF/BT results in local
   adjacency (e.g., local interface) over which the Ethernet frame is
   sent on.






Sajassi, et al.         Expires December 16, 2020              [Page 15]


Internet-Draft   Integrated Routing and Bridging in EVPN       June 2020


6.  Asymmetric IRB Procedures

6.1.  Control Plane - Advertising PE

   When a PE (e.g., PE1 in figure 4 above) learns MAC and IP address of
   an attached TS (e.g., via an ARP request), it populates its MAC-VRF/
   BT, IP-VRF, and ARP table just as in the case for symmetric IRB.  It
   then builds an EVPN MAC/IP Advertisement route (type 2) as follows
   and advertises it to other PEs participating in that tenant's VPN.

   o  The Length field of the BGP EVPN NLRI for an EVPN MAC/IP
      Advertisement route MUST be either 37 (if IPv4 address is carried)
      or 49 (if IPv6 address is carried).

   o  Route Distinguisher (RD), Ethernet Segment Identifier, Ethernet
      Tag ID, MAC Address Length, MAC Address, IP Address Length, IP
      Address, and MPLS Label1 fields MUST be set per [RFC7432] and
      [RFC8365].

   o  The MPLS Label2 field MUST NOT be included in this route.

   Just as in [RFC7432], the RD, Ethernet Tag ID, MAC Address Length,
   MAC Address, IP Address Length, and IP Address fields are part of the
   route key used by BGP to compare routes.  The rest of the fields are
   not part of the route key.

   This route is advertised along with the following extended community:

   o  Tunnel Type Extended Community

   For asymmetric IRB mode, Router's MAC EC is not needed because
   forwarding is performed using destination TS's MAC address which is
   carried in this EVPN route type-2 advertisement.

   This route MUST always be advertised with the MAC-VRF route target.
   It MAY also be advertised with a second route target corresponding to
   the IP-VRF.

6.2.  Control Plane - Receiving PE

   When a PE (e.g., PE2 in figure 4 above) receives this EVPN MAC/IP
   Advertisement route, it performs the following:

   o  Using MAC-VRF route target, it identifies the corresponding MAC-
      VRF and imports the MAC address into it.  For asymmetric IRB mode,
      it is assumed that all PEs participating in a tenant's VPN are
      configured with all subnets (i.e., all VLANs) and corresponding
      MAC-VRFs/BTs even if there are no locally attached TSes for some



Sajassi, et al.         Expires December 16, 2020              [Page 16]


Internet-Draft   Integrated Routing and Bridging in EVPN       June 2020


      of these subnets.  The reason for this is because ingress PE needs
      to do forwarding based on destination TS's MAC address and perform
      NVO tunnel encapsulation as a property of a lookup in MAC-VRF/BT.
      An implementation may choose to consolidate the lookup at the
      ingress PE's IP-VRF with the lookup at the ingress PE's
      destination subnet MAC-VRF.  Consideration for such consolidation
      of lookups is an implementation exercise and thus its
      specification is outside the scope of this document.

   o  If only MAC-VRF route target is used, then the receiving PE uses
      the MAC-VRF route target to identify the corresponding IP-VRF -
      i.e., many MAC-VRF route targets map to the same IP-VRF for a
      given tenant.  In this case, MAC-VRF may be used by the receiving
      PE to identify the corresponding IP VRF via the IRB interface
      associated with the subnet MAC-VRF/BT.  This would equivalent to
      how ARP table entries are typically mapped to IRB interface of an
      IP VRF for installing attached host routes in an IP VRF.  Since in
      asymmetric IRB mode, each PE is configured with all VLANs of a
      tenant, indirect import to IP VRF via the corresponding MAC-VRF
      route target is a viable alternative.

   o  Using MAC-VRF route target, the receiving PE identifies the
      corresponding ARP table for the tenant and it adds an entry to the
      ARP table for the TS's MAC and IP address association.  It should
      be noted that the tenant's ARP table at the receiving PE is
      identified by all the MAC- VRF route targets for that tenant.

   o  If IP-VRF route target is included, it may be used to import the
      route to IP-VRF.  If IP-VRF route-target is not included, MAC-VRF
      is used to derive corresponding IP-VRF for import, as explained in
      prior section.  In both cases, IP-VRF route is installed with the
      TS MAC binding included in the received route.

   If the receiving PE receives the MAC/IP Advertisement route with MPLS
   label2 field but the receiving PE only supports asymmetric IRB mode,
   then the receiving PE MUST ignore MPLS label2 field and install the
   MAC address in the corresponding MAC-VRF and (IP, MAC) association in
   the ARP table for that tenant (with IRB interface identified by the
   MAC-VRF).

   If the receiving PE receives the MAC/IP Advertisement route with MPLS
   label2 field and it can support symmetric IRB mode, then it should
   use the MAC-VRF route target to identify its corresponding MAC-VRF
   table and import the MAC address.  It should use the IP-VRF route
   target to identify the corresponding IP-VRF table and import the IP
   address, as specified in symmetric IRB handling.  It MUST NOT import
   (IP, MAC) association into its ARP table.




Sajassi, et al.         Expires December 16, 2020              [Page 17]


Internet-Draft   Integrated Routing and Bridging in EVPN       June 2020


6.3.  Data Plane - Ingress PE

   When an Ethernet frame is received by an ingress PE (e.g., PE1 in
   figure 4 above), the PE uses the AC ID (e.g., VLAN ID) to identify
   the associated MAC-VRF/BT and it performs a lookup on the destination
   MAC address.  If the MAC address corresponds to its IRB Interface MAC
   address, the ingress PE deduces that the packet must be inter-subnet
   routed.  Hence, the ingress PE performs an IP lookup in the
   associated IP-VRF table.  The lookup identifies a local adjacency to
   the IRB interface associated with the egress subnet's MAC-VRF/BT.

   The ingress PE gets the destination TS's MAC address for that TS's IP
   address from its ARP table, it encapsulates the packet with that
   destination MAC address and a source MAC address corresponding to
   that IRB interface and sends the packet to its destination subnet
   MAC-VRF/BT.

   The destination MAC address lookup in the MAC-VRF/BT results in BGP
   next hop address of egress PE along with label-1 (L2 VPN MPLS label
   or VNI).  The ingress PE encapsulates the packet using Ethernet NVO
   tunnel of the choice (e.g., VxLAN or GENEVE) and sends the packet to
   the egress PE.  Since the packet forwarding is between ingress PE's
   MAC-VRF/BT and egress PE's MAC-VRF/BT, the packet encapsulation
   procedures follows that of [RFC7432] for MPLS and [RFC8365] for VxLAN
   encapsulations.

6.4.  Data Plane - Egress PE

   When a tenant's Ethernet frame is received over an NVO tunnel by the
   egress PE, the egress PE removes NVO tunnel encapsulation and uses
   the VPN MPLS label (for MPLS encapsulation) or VNI (for NVO
   encapsulation) to identify the MAC-VRF/BT in which MAC lookup needs
   to be performed.

   The MAC lookup results in local adjacency (e.g., local interface)
   over which the packet needs to get sent.

   Note that the forwarding behavior on the egress PE is the same as
   EVPN intra-subnet forwarding described in [RFC7432] for MPLS and
   [RFC8365] for NVO networks.  In other words, all the packet
   processing associated with the inter-subnet forwarding semantics is
   confined to the ingress PE for asymmetric IRB mode.

   It should also be noted that [RFC7432] provides different level of
   granularity for the EVPN label.  Besides identifying bridge domain
   table, it can be used to identify the egress interface or a
   destination MAC address on that interface.  If EVPN label is used for
   egress interface or individual MAC address identification, then no



Sajassi, et al.         Expires December 16, 2020              [Page 18]


Internet-Draft   Integrated Routing and Bridging in EVPN       June 2020


   MAC lookup is needed in the egress PE for MPLS encapsulation and the
   packet can be directly forwarded to the egress interface just based
   on EVPN label lookup.

7.  Mobility Procedure

   When a TS moves from one NVE (aka source NVE) to another NVE (aka
   target NVE), it is important that the MAC mobility procedures are
   properly executed and the corresponding MAC-VRF and IP-VRF tables on
   all participating NVEs are updated.  [RFC7432] describes the MAC
   mobility procedures for L2-only services for both single-homed TS and
   multi-homed TS.  This section describes the incremental procedures
   and BGP Extended Communities needed to handle the MAC mobility for
   IRB.  In order to place the emphasis on the differences between
   L2-only and IRB use cases, the incremental procedure is described for
   single-homed TS with the expectation that the reader can easily
   extrapolate multi-homed TS based on the procedures described in
   section 15 of [RFC7432].  This section describes mobility procedures
   for both symmetric and asymmetric IRB.  Although the language used in
   this section is for IPv4 ARP, it equally applies to IPv6 ND.

   When a TS moves from a source NVE to a target NVE, it can behave in
   one of the following three ways:

   1.  TS initiates an ARP request upon a move to the target NVE

   2.  TS sends data packet without first initiating an ARP request to
       the target NVE

   3.  TS is a silent host and neither initiates an ARP request nor
       sends any packets

   The following subsections describe the procedures for each of the
   above options.  In the following subsections, it is assumed that the
   MAC and IP addresses of a TS have one-to-one relationship (i.e.,
   there is one IP address per MAC address and vice versa).  If there is
   many- to-one relationship such that there are many host IP addresses
   correspond to a single host MAC address or there are many host MAC
   addresses correspond to a single IP address, then to detect host
   mobility, the procedures in [IRB-EXT-MOBILITY] must be exercised
   followed by the procedures described below.

7.1.  Initiating an ARP Request upon a Move

   In this scenario when a TS moves from a source NVE to a target NVE,
   the TS initiates an ARP request upon the move (e.g., gratuitous ARP)
   to the target NVE.




Sajassi, et al.         Expires December 16, 2020              [Page 19]


Internet-Draft   Integrated Routing and Bridging in EVPN       June 2020


   The target NVE upon receiving this ARP request, updates its MAC-VRF,
   IP-VRF, and ARP table with the host MAC, IP, and local adjacency
   information (e.g., local interface).

   Since this NVE has previously learned the same MAC and IP addresses
   from the source NVE, it recognizes that there has been a MAC move and
   it initiates MAC mobility procedures per [RFC7432] by advertising an
   EVPN MAC/IP Advertisement route with both the MAC and IP addresses
   filled in (per sections 5.1 and 6.1) along with MAC Mobility Extended
   Community with the sequence number incremented by one.  The target
   NVE also exercises the MAC duplication detection procedure in section
   15.1 of [RFC7432].

   The source NVE upon receiving this MAC/IP Advertisement route,
   realizes that the MAC has moved to the target NVE.  It updates its
   MAC-VRF and IP-VRF table accordingly with the adjacency information
   of the target NVE.  In case of the asymmetric IRB, the source NVE
   also updates its ARP table with the received adjacency information
   and in case of the symmetric IRB, the source NVE removes the entry
   associated with the received (MAC, IP) from its local ARP table.  It
   then withdraws its EVPN MAC/IP Advertisement route.  Furthermore, it
   sends an ARP probe locally to ensure that the MAC is gone.  If an ARP
   response is received, the source NVE updates its ARP entry for that
   (IP, MAC) and re-advertises an EVPN MAC/IP Advertisement route for
   that (IP, MAC) along with MAC Mobility Extended Community with the
   sequence number incremented by one.  The source NVE also exercises
   the MAC duplication detection procedure in section 15.1 of [RFC7432].

   All other remote NVE devices upon receiving the MAC/IP Advertisement
   route with MAC Mobility extended community compare the sequence
   number in this advertisement with the one previously received.  If
   the new sequence number is greater than the old one, then they update
   the MAC/IP addresses of the TS in their corresponding MAC-VRF and IP-
   VRF tables to point to the target NVE.  Furthermore, upon receiving
   the MAC/IP withdraw for the TS from the source NVE, these remote PEs
   perform the cleanups for their BGP tables.

7.2.  Sending Data Traffic without an ARP Request

   In this scenario when a TS moves from a source NVE to a target NVE,
   the TS starts sending data traffic without first initiating an ARP
   request.

   The target NVE upon receiving the first data packet, learns the MAC
   address of the TS in data plane and updates its MAC-VRF table with
   the MAC address and the local adjacency information (e.g., local
   interface) accordingly.  The target NVE realizes that there has been




Sajassi, et al.         Expires December 16, 2020              [Page 20]


Internet-Draft   Integrated Routing and Bridging in EVPN       June 2020


   a MAC move because the same MAC address has been learned remotely
   from the source NVE.

   If EVPN-IRB NVEs are configured to advertise MAC-only routes in
   addition to MAC-and-IP EVPN routes, then the following steps are
   taken:

   o  The target NVE upon learning this MAC address in data-plane,
      updates this MAC address entry in the corresponding MAC-VRF with
      the local adjacency information (e.g., local interface).  It also
      recognizes that this MAC has moved and initiates MAC mobility
      procedures per [RFC7432] by advertising an EVPN MAC/IP
      Advertisement route with only the MAC address filled in along with
      MAC Mobility Extended Community with the sequence number
      incremented by one.

   o  The source NVE upon receiving this MAC/IP Advertisement route,
      realizes that the MAC has moved to the new NVE.  It updates its
      MAC-VRF table with the adjacency information for that MAC address
      to point to the target NVE and withdraws its EVPN MAC/IP
      Advertisement route that has only the MAC address (if it has
      advertised such route previously).  Furthermore, it searches for
      the corresponding MAC-IP entry and sends an ARP probe for this
      (MAC,IP) pair.  The ARP request message is sent both locally to
      all attached TSes in that subnet as well as it is sent to other
      NVEs participating in that subnet including the target NVE.  Note
      that the PE would need to maintain a correlation between MAC and
      MAC-IP route entries in the MAC-VRF to accomplish this.

   o  The target NVE passes the ARP request to its locally attached TSes
      and when it receives the ARP response, it updates its IP-VRF and
      ARP table with the host (MAC, IP) information.  It also sends an
      EVPN MAC/IP Advertisement route with both the MAC and IP addresses
      filled in along with MAC Mobility Extended Community with the
      sequence number set to the same value as the one for MAC-only
      advertisement route it sent previously.

   o  When the source NVE receives the EVPN MAC/IP Advertisement route,
      it updates its IP-VRF table with the new adjacency information
      (pointing to the target NVE).  In case of the asymmetric IRB, the
      source NVE also updates its ARP table with the received adjacency
      information and in case of the symmetric IRB, the source NVE
      removes the entry associated with the received (MAC, IP) from its
      local ARP table.  Furthermore, it withdraws its previously
      advertised EVPN MAC/IP route with both the MAC and IP address
      fields filled in.





Sajassi, et al.         Expires December 16, 2020              [Page 21]


Internet-Draft   Integrated Routing and Bridging in EVPN       June 2020


   o  All other remote NVE devices upon receiving the MAC/IP
      advertisement route with MAC Mobility extended community compare
      the sequence number in this advertisement with the one previously
      received.  If the new sequence number is greater than the old one,
      then they update the MAC/IP addresses of the TS in their
      corresponding MAC-VRF, IP-VRF, and ARP tables (in case of
      asymmetric IRB) to point to the new NVE.  Furthermore, upon
      receiving the MAC/IP withdraw for the TS from the old NVE, these
      remote PEs perform the cleanups for their BGP tables.

   If EVPN-IRB NVEs are configured not to advertise MAC-only routes,
   then upon receiving the first data packet, it learns the MAC address
   of the TS and updates the MAC entry in the corresponding MAC-VRF
   table with the local adjacency information (e.g., local interface).
   It also realizes that there has been a MAC move because the same MAC
   address has been learned remotely from the source NVE.  It uses the
   local MAC route to find the corresponding local MAC-IP route, and
   sends a unicast ARP request to the host and when receiving an ARP
   response, it follows the procedure outlined in section 7.1.  In the
   prior case, where MAC-only routes are also advertised, this procedure
   of triggering a unicast ARP probe at the target PE MAY also be used
   in addition to the source PE broadcast ARP probing procedure
   described earlier for better convergence.

7.3.  Silent Host

   In this scenario when a TS moves from a source NVE to a target NVE,
   the TS is silent and it neither initiates an ARP request nor it sends
   any data traffic.  Therefore, neither the target nor the source NVEs
   are aware of the MAC move.

   On the source NVE, an age-out timer (for the silent host that has
   moved) is used to trigger an ARP probe.  This age-out timer can be
   either ARP timer or MAC age-out timer and this is an implementation
   choice.  The ARP request gets sent both locally to all the attached
   TSes on that subnet as well as it gets sent to all the remote NVEs
   (including the target NVE) participating in that subnet.  The source
   NVE also withdraw the EVPN MAC/IP Advertisement route with only the
   MAC address (if it has previously advertised such a route).

   The target NVE passes the ARP request to its locally attached TSes
   and when it receives the ARP response, it updates its MAC-VRF, IP-
   VRF, and ARP table with the host (MAC, IP) and local adjacency
   information (e.g., local interface).  It also sends an EVPN MAC/IP
   advertisement route with both the MAC and IP address fields filled in
   along with MAC Mobility Extended Community with the sequence number
   incremented by one.




Sajassi, et al.         Expires December 16, 2020              [Page 22]


Internet-Draft   Integrated Routing and Bridging in EVPN       June 2020


   When the source NVE receives the EVPN MAC/IP Advertisement route, it
   updates its IP-VRF table with the new adjacency information (pointing
   to the target NVE).  In case of the asymmetric IRB, the source NVE
   also updates its ARP table with the received adjacency information
   and in case of the symmetric IRB, the source NVE removes the entry
   associated with the received (MAC, IP) from its local ARP table.
   Furthermore, it withdraws its previously advertised EVPN MAC/IP route
   with both the MAC and IP address fields filled in.

   All other remote NVE devices upon receiving the MAC/IP Advertisement
   route route with MAC Mobility extended community compare the sequence
   number in this advertisement with the one previously received.  If
   the new sequence number is greater than the old one, then they update
   the MAC/IP addresses of the TS in their corresponding MAC-VRF, IP-
   VRF, and ARP (in case of asymmetric IRB) tables to point to the new
   NVE.  Furthermore, upon receiving the MAC/IP withdraw for the TS from
   the old NVE, these remote PEs perform the cleanups for their BGP
   tables.

8.  BGP Encoding

   This document defines one new BGP Extended Community for EVPN.

8.1.  Router's MAC Extended Community

   A new EVPN BGP Extended Community called Router's MAC is introduced
   here.  This new extended community is a transitive extended community
   with the Type field of 0x06 (EVPN) and the Sub-Type of 0x03.  It may
   be advertised along with BGP Encapsulation Extended Community defined
   in section 4.5 of [TUNNEL-ENCAP].

   The Router's MAC Extended Community is encoded as an 8-octet value as
   follows:


        0                   1                   2                   3
        0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       | Type=0x06     | Sub-Type=0x03 |        Router's MAC           |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                      Router's MAC Cont'd                      |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

               Figure 5: Router's MAC Extended Community


   This extended community is used to carry the PE's MAC address for
   symmetric IRB scenarios and it is sent with RT-2.



Sajassi, et al.         Expires December 16, 2020              [Page 23]


Internet-Draft   Integrated Routing and Bridging in EVPN       June 2020


9.  Operational Models for Symmetric Inter-Subnet Forwarding

   The following sections describe two main symmetric IRB forwarding
   scenarios (within a DC - i.e., intra-DC) along with the corresponding
   procedures.  In the following scenarios, without loss of generality,
   it is assumed that a given tenant is represented by a single IP-VPN
   instance.  Therefore, on a given PE, a tenant is represented by a
   single IP-VRF table and one or more MAC-VRF tables.

9.1.  IRB forwarding on NVEs for Tenant Systems

   This section covers the symmetric IRB procedures for the scenario
   where each Tenant System (TS) is attached to one or more NVEs and its
   host IP and MAC addresses are learned by the attached NVEs and are
   distributed to all other NVEs that are interested in participating in
   both intra-subnet and inter-subnet communications with that TS.

   In this scenario, without loss of generality, it is assumed that NVEs
   operate in VLAN-based service interface mode with one Bridge
   Table (BT) per MAC-VRF.  Thus, for a given tenant, an NVE has one
   MAC-VRF for each tenant subnet (e.g., each VLAN) that is configured
   for extension via VxLAN or GENEVE encapsulation.  In case of VLAN-
   aware bundling, then each MAC-VRF consists of multiple Bridge Tables
   (e.g., one BT per VLAN).  The MAC-VRFs on an NVE for a given tenant
   are associated with an IP-VRF corresponding to that tenant (or IP-VPN
   instance) via their IRB interfaces.

   Since VxLAN and GENEVE encapsulations require inner Ethernet header
   (inner MAC SA/DA), and since for inter-subnet traffic, TS MAC address
   cannot be used, the ingress NVE's MAC address is used as inner MAC
   SA.  The NVE's MAC address is the device MAC address and it is common
   across all MAC-VRFs and IP-VRFs.  This MAC address is advertised
   using the new EVPN Router's MAC Extended Community (section 8.1).

   Figure 6 below illustrates this scenario where a given tenant (e.g.,
   an IP-VPN instance) has three subnets represented by MAC-VRF1, MAC-
   VRF2, and MAC-VRF3 across two NVEs.  There are five TSes that are
   associated with these three MAC-VRFs - i.e., TS1, TS4, and TS5 are on
   the same subnet (e.g., same MAC-VRF/VLAN).  TS1 and TS5 are
   associated with MAC-VRF1 on NVE1, while TS4 is associated with MAC-
   VRF1 on NVE2.  TS2 is associated with MAC-VRF2 on NVE1, and TS3 is
   associated with MAC-VRF3 on NVE2.  MAC-VRF1 and MAC-VRF2 on NVE1 are
   in turn associated with IP-VRF1 on NVE1 and MAC-VRF1 and MAC-VRF3 on
   NVE2 are associated with IP-VRF1 on NVE2.  When TS1, TS5, and TS4
   exchange traffic with each other, only L2 forwarding (bridging) part
   of the IRB solution is exercised because all these TSes belong to the
   same subnet.  However, when TS1 wants to exchange traffic with TS2 or
   TS3 which belong to different subnets, both bridging and routing



Sajassi, et al.         Expires December 16, 2020              [Page 24]


Internet-Draft   Integrated Routing and Bridging in EVPN       June 2020


   parts of the IRB solution are exercised.  The following subsections
   describe the control and data planes operations for this IRB scenario
   in details.


                     NVE1         +---------+
               +-------------+    |         |
       TS1-----|         MACx|    |         |        NVE2
     (IP1/M1)  |(MAC-        |    |         |   +-------------+
       TS5-----| VRF1)\      |    |  MPLS/  |   |MACy  (MAC-  |-----TS3
     (IP5/M5)  |       \     |    |  VxLAN/ |   |     / VRF3) | (IP3/M3)
               |    (IP-VRF1)|----|  NVGRE  |---|(IP-VRF1)    |
               |       /     |    |         |   |     \       |
       TS2-----|(MAC- /      |    |         |   |      (MAC-  |-----TS4
     (IP2/M2)  | VRF2)       |    |         |   |       VRF1) | (IP4/M4)
               +-------------+    |         |   +-------------+
                                  |         |
                                  +---------+

          Figure 6: IRB forwarding on NVEs for Tenant Systems


9.1.1.  Control Plane Operation

   Each NVE advertises a MAC/IP Advertisement route (i.e., Route Type 2)
   for each of its TSes with the following field set:

   o  RD and ESI per [RFC7432]

   o  Ethernet Tag = 0; assuming VLAN-based service

   o  MAC Address Length = 48

   o  MAC Address = Mi ; where i = 1,2,3,4, or 5 in the above example

   o  IP Address Length = 32 or 128

   o  IP Address = IPi ; where i = 1,2,3,4, or 5 in the above example

   o  Label-1 = MPLS Label or VNI corresponding to MAC-VRF

   o  Label-2 = MPLS Label or VNI corresponding to IP-VRF

   Each NVE advertises an RT-2 route with two Route Targets (one
   corresponding to its MAC-VRF and the other corresponding to its IP-
   VRF.  Furthermore, the RT-2 is advertised with two BGP Extended
   Communities.  The first BGP Extended Community identifies the tunnel
   type per section 4.5 of [TUNNEL-ENCAP] and the second BGP Extended



Sajassi, et al.         Expires December 16, 2020              [Page 25]


Internet-Draft   Integrated Routing and Bridging in EVPN       June 2020


   Community includes the MAC address of the NVE (e.g., MACx for NVE1 or
   MACy for NVE2) as defined in section 8.1.  This second Extended
   Community (for the MAC address of NVE) is only required when Ethernet
   NVO tunnel type is used.  If IP NVO tunnel type is used, then there
   is no need to send this second Extended Community.  It should be
   noted that IP NVO tunnel type is only applicable to symmetric IRB
   procedures.

   Upon receiving this advertisement, the receiving NVE performs the
   following:

   o  It uses Route Targets corresponding to its MAC-VRF and IP-VRF for
      identifying these tables and subsequently importing the MAC and IP
      addresses into them respectively.

   o  It imports the MAC address from MAC/IP Advertisement route into
      the MAC-VRF with BGP Next Hop address as underlay tunnel
      destination address (e.g., VTEP DA for VxLAN encapsulation) and
      Label-1 as VNI for VxLAN encapsulation or EVPN label for MPLS
      encapsulation.

   o  If the route carries the new Router's MAC Extended Community, and
      if the receiving NVE uses Ethernet NVO tunnel, then the receiving
      NVE imports the IP address into IP-VRF with NVE's MAC address
      (from the new Router's MAC Extended Community) as inner MAC DA and
      BGP Next Hop address as underlay tunnel destination address, VTEP
      DA for VxLAN encapsulation and Label-2 as IP-VPN VNI for VxLAN
      encapsulation.

   o  If the receiving NVE ration MPLS encapsulation, then the receiving
      NVE imports the IP address into IP-VRF with BGP Next Hop address
      as underlay tunnel destination address, and Label-2 as IP-VPN
      label for MPLS encapsulation.

   If the receiving NVE receives a RT-2 with only Label-1 and only a
   single Route Target corresponding to IP-VRF, or if it receives a RT-2
   with only a single Route Target corresponding to MAC-VRF but with
   both Label-1 and Label-2, or if it receives a RT-2 with MAC Address
   Length of zero, then it MUST treat the route as withdraw [RFC7606]
   and log an error message.

9.1.2.  Data Plane Operation

   The following description of the data-plane operation describes just
   the logical functions and the actual implementation may differ.  Lets
   consider data-plane operation when TS1 in subnet-1 (MAC-VRF1) on NVE1
   wants to send traffic to TS3 in subnet-3 (MAC-VRF3) on NVE2.




Sajassi, et al.         Expires December 16, 2020              [Page 26]


Internet-Draft   Integrated Routing and Bridging in EVPN       June 2020


   o  NVE1 receives a packet with MAC DA corresponding to the MAC-VRF1
      IRB interface on NVE1 (the interface between MAC-VRF1 and IP-
      VRF1), and VLAN-tag corresponding to MAC-VRF1.

   o  Upon receiving the packet, the NVE1 uses VLAN-tag to identify the
      MAC-VRF1.  It then looks up the MAC DA and forwards the frame to
      its IRB interface.

   o  The Ethernet header of the packet is stripped and the packet is
      fed to the IP-VRF where IP lookup is performed on the destination
      IP address.  This lookup yields the outgoing NVO tunnel and the
      required encapsulation.  If the encapsulation is for Ethernet NVO
      tunnel, then it includes the egress NVE's MAC address as inner MAC
      DA, the egress NVE's IP address (e.g., BGP Next Hop address) as
      the VTEP DA, and the VPN-ID as the VNI.  The inner MAC SA and VTEP
      SA are set to NVE's MAC and IP addresses respectively.  If it is a
      MPLS encapsulation, then corresponding EVPN and LSP labels are
      added to the packet.  The packet is then forwarded to the egress
      NVE.

   o  On the egress NVE, if the packet arrives on Ethernet NVO tunnel
      (e.g., it is VxLAN encapsulated), then the NVO tunnel header is
      removed.  Since the inner MAC DA is the egress NVE's MAC address,
      the egress NVE knows that it needs to perform an IP lookup.  It
      uses the VNI to identify the IP-VRF table.  If the packet is MPLS
      encapsulated, then the EVPN label lookup identifies the IP-VRF
      table.  Next, an IP lookup is performed for the destination TS
      (TS3) which results in access-facing IRB interface over which the
      packet is sent.  Before sending the packet over this interface,
      the ARP table is consulted to get the destination TS's MAC
      address.

   o  The IP packet is encapsulated with an Ethernet header with MAC SA
      set to that of IRB interface MAC address (i.e, IRB interface
      between MAC-VRF3 and IP-VRF1 on NVE2) and MAC DA set to that of
      destination TS (TS3) MAC address.  The packet is sent to the
      corresponding MAC-VRF (i.e., MAC-VRF3) and after a lookup of MAC
      DA, is forwarded to the destination TS (TS3) over the
      corresponding interface.

   In this symmetric IRB scenario, inter-subnet traffic between NVEs
   will always use the IP-VRF VNI/MPLS label.  For instance, traffic
   from TS2 to TS4 will be encapsulated by NVE1 using NVE2's IP-VRF VNI/
   MPLS label, as long as TS4's host IP is present in NVE1's IP-VRF.







Sajassi, et al.         Expires December 16, 2020              [Page 27]


Internet-Draft   Integrated Routing and Bridging in EVPN       June 2020


9.2.  IRB forwarding on NVEs for Subnets behind Tenant Systems

   This section covers the symmetric IRB procedures for the scenario
   where some Tenant Systems (TSes) support one or more subnets and
   these TSes are associated with one or more NVEs.  Therefore, besides
   the advertisement of MAC/IP addresses for each TS which can be multi-
   homed with All-Active redundancy mode, the associated NVE needs to
   also advertise the subnets statically configured on each TS.

   The main difference between this solution and the previous one is the
   additional advertisement corresponding to each subnet.  These subnet
   advertisements are accomplished using EVPN IP Prefix route defined in
   [EVPN-PREFIX].  These subnet prefixes are advertised with the IP
   address of their associated TS (which is in overlay address space) as
   their next hop.  The receiving NVEs perform recursive route
   resolution to resolve the subnet prefix with its associated ingress
   NVE so that they know which NVE to forward the packets to when they
   are destined for that subnet prefix.

   The advantage of this recursive route resolution is that when a TS
   moves from one NVE to another, there is no need to re-advertise any
   of the subnet prefixes for that TS.  All it is needed is to advertise
   the IP/MAC addresses associated with the TS itself and exercise MAC
   mobility procedures for that TS.  The recursive route resolution
   automatically takes care of the updates for the subnet prefixes of
   that TS.

   Figure below illustrates this scenario where a given tenant (e.g., an
   IP-VPN service) has three subnets represented by MAC-VRF1, MAC-VRF2,
   and MAC-VRF3 across two NVEs.  There are four TSes associated with
   these three MAC-VRFs - i.e., TS1, TS5 are connected to MAC-VRF1 on
   NVE1, TS2 is connected to MAC-VRF2 on NVE1, TS3 is connected to MAC-
   VRF3 on NVE2, and TS4 is connected to MAC-VRF1 on NVE2.  TS1 has two
   subnet prefixes (SN1 and SN2) and TS3 has a single subnet prefix,
   SN3.  The MAC-VRFs on each NVE are associated with their
   corresponding IP-VRF using their IRB interfaces.  When TS4 and TS1
   exchange intra- subnet traffic, only L2 forwarding (bridging) part of
   the IRB solution is used (i.e., the traffic only goes through their
   MAC- VRFs); however, when TS3 wants to forward traffic to SN1 or SN2
   sitting behind TS1 (inter-subnet traffic), then both bridging and
   routing parts of the IRB solution are exercised (i.e., the traffic
   goes through the corresponding MAC-VRFs and IP-VRFs).  The following
   subsections describe the control and data planes operations for this
   IRB scenario in details.







Sajassi, et al.         Expires December 16, 2020              [Page 28]


Internet-Draft   Integrated Routing and Bridging in EVPN       June 2020


                                NVE1      +----------+
        SN1--+          +-------------+   |          |
             |--TS1-----|(MAC- \      |   |          |
        SN2--+ IP1/M1   | VRF1) \     |   |          |
                        |     (IP-VRF)|---|          |
                        |       /     |   |          |
                TS2-----|(MAC- /      |   |  MPLS/   |
               IP2/M2   | VRF2)       |   |  VxLAN/  |
                        +-------------+   |  NVGRE   |
                        +-------------+   |          |
        SN3--+--TS3-----|(MAC-\       |   |          |
               IP3/M3   | VRF3)\      |   |          |
                        |     (IP-VRF)|---|          |
                        |       /     |   |          |
                TS4-----|(MAC- /      |   |          |
               IP4/M4   | VRF1)       |   |          |
                        +-------------+   +----------+
                               NVE2


           Figure 7: IRB forwarding on NVEs for subnets behind TSes


9.2.1.  Control Plane Operation

   Each NVE advertises a Route Type-5 (RT-5, IP Prefix Route defined in
   [EVPN-PREFIX]) for each of its subnet prefixes with the IP address of
   its TS as the next hop (gateway address field) as follow:

   o  RD associated with the IP-VRF

   o  ESI = 0

   o  Ethernet Tag = 0;

   o  IP Prefix Length = 0 to 32 or 0 to 128

   o  IP Prefix = SNi

   o  Gateway Address = IPi; IP address of TS

   o  Label = 0

   This RT-5 is advertised with one or more Route Targets that have been
   configured as "export route targets" of the IP-VRF from which the
   route is originated.





Sajassi, et al.         Expires December 16, 2020              [Page 29]


Internet-Draft   Integrated Routing and Bridging in EVPN       June 2020


   Each NVE also advertises an RT-2 (MAC/IP Advertisement Route) along
   with their associated Route Targets and Extended Communities for each
   of its TSes exactly as described in section 9.1.1.

   Upon receiving the RT-5 advertisement, the receiving NVE performs the
   following:

   o  It uses the Route Target to identify the corresponding IP-VRF

   o  It imports the IP prefix into its corresponding IP-VRF that is
      configured with an import RT that is one of the RTs being carried
      by the RT-5 route along with the IP address of the associated TS
      as its next hop.

   When receiving the RT-2 advertisement, the receiving NVE imports MAC/
   IP addresses of the TS into the corresponding MAC-VRF and IP-VRF per
   section 9.1.1.  When both routes exist, recursive route resolution is
   performed to resolve the IP prefix (received in RT-5) to its
   corresponding NVE's IP address (e.g., its BGP next hop).  BGP next
   hop will be used as underlay tunnel destination address (e.g., VTEP
   DA for VxLAN encapsulation) and Router's MAC will be used as inner
   MAC for VxLAN encapsulation.

9.2.2.  Data Plane Operation

   The following description of the data-plane operation describes just
   the logical functions and the actual implementation may differ.  Lets
   consider data-plane operation when a host on SN1 sitting behind TS1
   wants to send traffic to a host sitting behind SN3 behind TS3.

   o  TS1 send a packet with MAC DA corresponding to the MAC-VRF1 IRB
      interface of NVE1, and VLAN-tag corresponding to MAC-VRF1.

   o  Upon receiving the packet, the ingress NVE1 uses VLAN-tag to
      identify the MAC-VRF1.  It then looks up the MAC DA and forwards
      the frame to its IRB interface just like section 9.1.1.

   o  The Ethernet header of the packet is stripped and the packet is
      fed to the IP-VRF; where, IP lookup is performed on the
      destination address.  This lookup yields the fields needed for
      VxLAN encapsulation with NVE2's MAC address as the inner MAC DA,
      NVE'2 IP address as the VTEP DA, and the VNI.  MAC SA is set to
      NVE1's MAC address and VTEP SA is set to NVE1's IP address.

   o  The packet is then encapsulated with the proper header based on
      the above info and is forwarded to the egress NVE (NVE2).





Sajassi, et al.         Expires December 16, 2020              [Page 30]


Internet-Draft   Integrated Routing and Bridging in EVPN       June 2020


   o  On the egress NVE (NVE2), assuming the packet is VxLAN
      encapsulated, the VxLAN and the inner Ethernet headers are removed
      and the resultant IP packet is fed to the IP-VRF associated with
      that the VNI.

   o  Next, a lookup is performed based on IP DA (which is in SN3) in
      the associated IP-VRF of NVE2.  The IP lookup yields the access-
      facing IRB interface over which the packet needs to be sent.
      Before sending the packet over this interface, the ARP table is
      consulted to get the destination TS (TS3) MAC address.

   o  The IP packet is encapsulated with an Ethernet header with the MAC
      SA set to that of the access-facing IRB interface of the egress
      NVE (NVE2) and the MAC DA is set to that of destination TS (TS3)
      MAC address.  The packet is sent to the corresponding MAC-VRF3 and
      after a lookup of MAC DA, is forwarded to the destination TS (TS3)
      over the corresponding interface.

10.  Acknowledgements

   The authors would like to thank Sami Boutros, Jeffrey Zhang,
   Krzysztof Szarkowicz, Lukas Krattiger and Neeraj Malhotra for their
   valuable comments.  The authors would also like to thank Linda
   Dunbar, Florin Balus, Yakov Rekhter, Wim Henderickx, Lucy Yong, and
   Dennis Cai for their feedbacks and contributions.

11.  Security Considerations

   This document describes a set of procedures for Inter-Subnet
   Forwarding of tenant traffic across PEs (or NVEs).  These procedures
   include both layer-2 forwarding and layer-3 routing on a packet by
   packet basis.  The security consideration for layer-2 forwarding in
   this document follow that of [RFC7432] for MPLS encapsulation and it
   follows that of [RFC8365] for VxLAN or GENEVE encapsulations.

   Furthermore, the security consideration for layer-3 routing is this
   document follows that of [RFC4365] with the exception for application
   of routing protocols between CEs and PEs.  Contrary to [RFC4364],
   this document does not describe route distribution techniques between
   CEs and PEs, but rather considers the CEs as TSes or VAs that do not
   run dynamic routing protocols.  This can be considered a security
   advantage, since dynamic routing protocols can be blocked on the NVE/
   PE ACs, not allowing the tenant to interact with the infrastructure's
   dynamic routing protocols.

   In this document, the RT-5 is used for certain scenarios.  This route
   uses an Overlay Index that requires a recursive resolution to a
   different EVPN route (an RT-2).  Because of this, it is worth noting



Sajassi, et al.         Expires December 16, 2020              [Page 31]


Internet-Draft   Integrated Routing and Bridging in EVPN       June 2020


   that any action that ends up filtering or modifying the RT-2 route
   used to convey the Overlay Indexes, will modify the resolution of the
   RT-5 and therefore the forwarding of packets to the remote subnet.

12.  IANA Considerations

   IANA has allocated a new transitive extended community Type of 0x06
   and Sub-Type of 0x03 for EVPN Router's MAC Extended Community.

13.  Intellectual Property Considerations

   This document is being submitted for use in IETF standards
   discussions.

14.  References

14.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC4364]  Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private
              Networks (VPNs)", RFC 4364, DOI 10.17487/RFC4364, February
              2006, <https://www.rfc-editor.org/info/rfc4364>.

   [RFC7432]  Sajassi, A., Ed., Aggarwal, R., Bitar, N., Isaac, A.,
              Uttaro, J., Drake, J., and W. Henderickx, "BGP MPLS-Based
              Ethernet VPN", RFC 7432, DOI 10.17487/RFC7432, February
              2015, <https://www.rfc-editor.org/info/rfc7432>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

   [RFC8214]  Boutros, S., Sajassi, A., Salam, S., Drake, J., and J.
              Rabadan, "Virtual Private Wire Service Support in Ethernet
              VPN", RFC 8214, DOI 10.17487/RFC8214, August 2017,
              <https://www.rfc-editor.org/info/rfc8214>.

14.2.  Informative References

   [I-D.ietf-bess-evpn-prefix-advertisement]
              Rabadan, J., Henderickx, W., Drake, J., Lin, W., and A.
              Sajassi, "IP Prefix Advertisement in EVPN", draft-ietf-
              bess-evpn-prefix-advertisement-11 (work in progress), May
              2018.



Sajassi, et al.         Expires December 16, 2020              [Page 32]


Internet-Draft   Integrated Routing and Bridging in EVPN       June 2020


   [RFC4365]  Rosen, E., "Applicability Statement for BGP/MPLS IP
              Virtual Private Networks (VPNs)", RFC 4365,
              DOI 10.17487/RFC4365, February 2006,
              <https://www.rfc-editor.org/info/rfc4365>.

   [RFC5798]  Nadas, S., Ed., "Virtual Router Redundancy Protocol (VRRP)
              Version 3 for IPv4 and IPv6", RFC 5798,
              DOI 10.17487/RFC5798, March 2010,
              <https://www.rfc-editor.org/info/rfc5798>.

   [RFC7348]  Mahalingam, M., Dutt, D., Duda, K., Agarwal, P., Kreeger,
              L., Sridhar, T., Bursell, M., and C. Wright, "Virtual
              eXtensible Local Area Network (VXLAN): A Framework for
              Overlaying Virtualized Layer 2 Networks over Layer 3
              Networks", RFC 7348, DOI 10.17487/RFC7348, August 2014,
              <https://www.rfc-editor.org/info/rfc7348>.

   [RFC7365]  Lasserre, M., Balus, F., Morin, T., Bitar, N., and Y.
              Rekhter, "Framework for Data Center (DC) Network
              Virtualization", RFC 7365, DOI 10.17487/RFC7365, October
              2014, <https://www.rfc-editor.org/info/rfc7365>.

   [RFC7606]  Chen, E., Ed., Scudder, J., Ed., Mohapatra, P., and K.
              Patel, "Revised Error Handling for BGP UPDATE Messages",
              RFC 7606, DOI 10.17487/RFC7606, August 2015,
              <https://www.rfc-editor.org/info/rfc7606>.

Authors' Addresses

   Ali Sajassi
   Cisco Systems
   MILPITAS, CALIFORNIA 95035
   UNITED STATES

   Email: sajassi@cisco.com


   Samer Salam
   Cisco Systems

   Email: ssalam@cisco.com


   Samir Thoria
   Cisco Systems

   Email: sthoria@cisco.com




Sajassi, et al.         Expires December 16, 2020              [Page 33]


Internet-Draft   Integrated Routing and Bridging in EVPN       June 2020


   John E Drake
   Juniper

   Email: jdrake@juniper.net


   Jorge Rabadan
   Nokia

   Email: jorge.rabadan@nokia.com









































Sajassi, et al.         Expires December 16, 2020              [Page 34]


Html markup produced by rfcmarkup 1.129d, available from https://tools.ietf.org/tools/rfcmarkup/