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Versions: 00 01 02 03 04 05 RFC 2338

INTERNET-DRAFT                                                 S. Knight
June 22, 1997                                Ascend Communications, Inc.
                                                               D. Weaver
                                             Ascend Communications, Inc.
                                                              D. Whipple
                                                         Microsoft, Inc.
                                                               R. Hinden
                                                  Ipsilon Networks, Inc.






                   Virtual Router Redundancy Protocol

                     <draft-ietf-vrrp-spec-00.txt>



Status of this Memo

   This document is an Internet-Draft.  Internet-Drafts are working
   documents of the Internet Engineering Task Force (IETF), its areas,
   and its working groups.  Note that other groups may also distribute
   working documents as Internet-Drafts.

   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.''

   To learn the current status of any Internet-Draft, please check the
   ``1id-abstracts.txt'' listing contained in the Internet- Drafts
   Shadow Directories on ds.internic.net (US East Coast), nic.nordu.net
   (Europe), ftp.isi.edu (US West Coast), or munnari.oz.au (Pacific
   Rim).

   This internet draft expires on December 23, 1997.

Abstract

   The memo documents the Virtual Router Redundancy Protocol.  This is a
   protocol which allows several routers to utilize the same virtual IP
   address.  One router will be elected as a master, with X routers
   acting as backups in case of failure of the master router.  The
   primary advantage to utilizing this protocol, is that host systems
   may be configured with a single default gateway, rather than running



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   an active routing protocol.  Each interface on each router within a
   VRRP cluster, will be configured with a real IP address, and the
   virtual IP address for the particular cluster.  Overall, this
   protocol adds to the options for providing fault redundancy for
   router networks.


Table Of Contents

   1.  Introduction...............................................3
   2.  Scope......................................................3
   3.  Definitions................................................4
   4.  Sample Configurations......................................4
      4.1   Sample Configuration 1................................4
      4.2   Sample Configuration 2................................5
   5.  Protocol...................................................6
      5.1   VRRP Packet Format....................................6
      5.2   IP Field Descriptions.................................6
      5.3   VRRP Field Descriptions...............................7
   6.  Protocol State Machine.....................................9
      6.1 Parameters..............................................9
      6.2 Timers.................................................10
      6.3  State Transition Diagram..............................10
      6.4  State Descriptions....................................10
      6.5  State Table...........................................12
   7.  Sending and Receiving VRRP Packets........................14
      7.1  Receiving VRRP Packets................................14
      7.2 Transmitting Packets...................................14
      7.3 Virtual MAC Address....................................15
   8.  Host Operation............................................15
      8.1   Host ARP Requests....................................15
   9.  Operational Issues........................................15
      9.1 ICMP Redirects.........................................15
      9.2 Proxy ARP..............................................15
      9.3 Network Management.....................................16
   10. Operation over Token Ring.................................16
   11. References................................................17
   12. Security Considerations...................................17
   13. Authors' Addresses........................................17
   14. Acknowledgments...........................................17
   15. Changes from Previous Drafts..............................18










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1.  Introduction

   The reason for the development of VRRP is to create a standard
   protocol, with multi-vendor support to resolve the problem of router
   failure.  Specifically, when a single router is utilized as a default
   gateway, and all hosts are statically configured to this default
   gateway, a failure is catastrophic.  VRRP resolves this problem by
   creating virtual clusters, where each cluster is configured with a
   set of member routers.  Each member router is either a master router
   for the cluster or a backup router for the cluster, but not both
   simultaneously. In addition, there MUST only be a single master
   router per cluster, at any given time. All member routers are
   configured to be part of a cluster, with a given virtual IP address.
   This virtual IP address is utilized as the default gateway on all of
   the host systems.  Given a failure on the current master router, the
   next appropriate backup router will become the master router for the
   given cluster.  When routers are configured with the equal priority
   the router which is master will stay master as long as it is up.

   Of course this problem could be solved by running a standard routing
   protocol such as OSPF, RIP, or RIPv2 on the hosts.  However, this is
   not always feasible due to either security issues, when hosts are
   multihomed, or in some cases implementations of these routing
   protocols simply do not exist.

   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].


2.  Scope

   This memo describes the Virtual Router Redundancy Protocol.

   This protocol is intended for IPv4 only.  A version for IPv6 will be
   defined in a separate specification.

   Within the scope of this specification are:

      1.  Packet format and header contents.
      2.  State Diagrams and Descriptions
      3.  Network Design Samples

   Outside of the scope are

      1.  Network management
      2.  Host internal optimizations




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3.  Definitions

   Cluster

      Used to describe a set of routers who all have membership to the
      set of routers S, where S contains all routers configured with
      the same virtual IP address.

   Master Router

      Used to describe the currently active router, for a particular
      cluster, with a particular virtual IP address.  Their can only be
      one master router in a particular cluster.

   Backup Router

      Used to describe a router which is configured to act as a backup
      for a particular cluster.  There can be several backup routers in
      a single cluster.


4.  Sample Configurations

4.1  Sample Configuration 1

   The following figure shows a simple VRRP network.

                       +--------------------------+
                       |        Cluster X         |
                       |                          |
                       |   +-----+      +-----+   |
                       |   | MRX |      | BRX |   |
                       |   +-----+      +-----+   |
         Real IP 1 ---------->*            *<---------- Real IP 2
                       |      |      *     |      |
                       +-------------^------------+
                              |      |     |
           -------------------+------|-----+-----+-------------+------
                                     |           ^             ^
                 Virtual IP --(VIPX)-+         (VIPX)        (VIPX)
                                                 |             |
                                              +--+--+       +--+--+
                                              |  H1 |       |  H2 |
                                              +-----+       +-----+

   The above configuration shows the most likely utilization of the VRRP
   protocol. In this configuration, the hosts simply point their default
   routes at the virtual IP address X (VIPX), and the routers run VRRP



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   between themselves.  The router on the left is the default master
   router (MRX), and the router on the right is the backup router (BRX).

      Legend:  ---+---+---+--  =  802 network, Ethernet or FDDI
                            H  =  Host computer
                           MR  =  Master Router
                           BR  =  Backup Router
                            *  =  IP Address
                          VIP  =  default gateway for hosts (Virtual IP)


4.2  Sample Configuration 2

   The following figure shows a more interesting VRRP network.

                  +--------------------------+
                  | Cluster X and Cluster Y  |
                  |                          |
                  |   +-----+      +-----+   |
                  |   | MRX |      | BRX |   |
                  |   |  &  |      |  &  |   |
                  |   | BRY |      | MRY |   |
                  |   +-----+      +-----+   |
    Real IP 1 ---------->*            *<---------- Real IP 2
                  |      |  *      *  |      |
                  +---------^------^---------+
                         |  |      |  |
       ------------------+--|------|--+-----+--------+--------+--------+--
                            |      |        ^        ^        ^        ^
        Virtual IP --(VIPX)-+      |      (VIPX)   (VIPY)   (VIPX)   (VIPY)
                                   |        |        |        |        |
        Virtual IP --(VIPY)--------+     +--+--+  +--+--+  +--+--+  +--+--+
                                         |  H1 |  |  H2 |  |  H3 |  |  H4 |
                                         +-----+  +-----+  +--+--+  +--+--+

   In the above configuration, half of the hosts point their default
   gateway at cluster X's virtual IP address (VIPX), and half the hosts
   point their default gateway at cluster Y's virtual IP address (VIPY).
   This has the effect of load balancing the outgoing traffic, while
   also providing full redundancy.

      Legend:  ---+---+---+--  =  802 network, Ethernet or FDDI
                            H  =  Host computer
                           MR  =  Master Router
                           BR  =  Backup Router
                            *  =  IP Address
                          VIP  =  default gateway for hosts (Virtual IP)




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5.  Protocol

   The purpose of the VRRP packet is to communicate to all other VRRP
   routers both the priority and the state of the master's associated
   interface.

   VRRP packets are sent encapsulated in IP packets.  They are sent to
   an IPv4 multicast address assigned for VRRP.

5.1  VRRP Packet Format

   This section defines the format of the VRRP packet and the relevant
   fields in the IP header.

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    0 |    Version    | VRRP Cluster  |   Priority    |     Type      |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    1 |   Auth Type   |   Adver Int   |          Checksum             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    2 |                      Virtual IP address                       |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    3 |                      Authentication Data                      |
      +---------------------------------------------------------------+
    4 |                                                               |
      +---------------------------------------------------------------+


5.2  IP Field Descriptions

5.2.1  Source Address

   The real IP address of the interface the packet is being sent from.

5.2.2  Destination Address

   The VRRP IP multicast address assigned by the IANA.  It is defined to
   be:

       224.0.0.(TBD IANA assignment)

   This is a link local scope multicast address.  Routers should not
   forward a datagram with this destination address regardless of its
   TTL.






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5.2.3  TTL

   The TTL should be set to 255.  A VRRP router receiving a packet with
   the TTL not equal to 255 MUST discard the packet.

5.2.4  Protocol

   The VRRP IP protocol number assigned by the IANA.  It is defined to
   be (TBD).

5.3 VRRP Field Descriptions

5.3.1  Version

   The version field specifies the VRRP protocol version of this packet.
   This document defines version 1.

5.3.2  VRRP Cluster

   The VRRP Cluster field specifies the cluster this packet applies to.
   Note:  The interface may participate in more than one VRRP cluster
   simultaneously, perhaps serving as master in one cluster, while
   simultaneously serving as backup in other clusters.

5.3.3  Priority

   The priority field specifies the currently configured VRRP priority
   value for this interface and cluster.  Higher values equal higher
   priority.  This field is an 8 bit unsigned field, giving 1 as the
   minimum priority, and 255 as the maximum priority.  The default
   priority is 100 (decimal).

   Priority value of zero (0) has a special meaning.  It means that the
   current master had decided to stop running VRRP.  This is used to
   cause other backup routers to quickly become master with out having
   to timeout the current master.

   In the event that two or more routers within a cluster have equal
   priority, and that priority is the highest priority in the cluster,
   initially the router with the higher real interface IP address
   (interpreted as a 32 bit unsigned integer) will become master.  Any
   new router joining the cluster with the same priority will not become
   master even if it has a higher IP address unless the current master
   goes down.







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5.3.4  Type

   The type field specifies the type of this VRRP packet.  The only
   packet type defined in this version of the protocol is:

       1      ADVERTISEMENT

   All other values are currently unknown, and if a packet is received
   with a value not listed, it should be discarded.

5.3.5  Authentication Type

   The authentication type field identifies the authentication method
   being utilized.  The current supported authentications are listed
   below:

      0 - No authentication
      1 - Simple text authentication
      2 - IP Security Option Authentication

   For simple text authentication any VRRP packet with an authentication
   string that does not match its configured authentication string
   should be discarded.

   The authentication type field is an 8 bit number and must be one of
   the above listed values.

5.3.5.1 IP Security Option Authentication

   When authentication is performed by using the IP Authentication
   Header as specified in [AUTH], the Authentication type should be set
   to "2".  If packet is received with the Authentication type set to
   "2" indicating IP security option authentication and no
   authentication header is present in the packet, the packet should be
   discarded.

5.3.6 Advertisement Interval (Adver Int)

   This field is the time interval for Master to Send ADVERTISEMENTS.
   Default is 1 second.  This field is used for troubleshooting
   misconfigured routers.

5.3.7 Checksum

   The checksum field is used to detect data corruption in the VRRP
   message.

   The checksum is the 16-bit one's complement of the one's complement



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   sum of the entire VRRP message starting with the version field.  For
   computing the checksum, the checksum field is set to zero.


5.3.8  Virtual IP address

   The virtual IP address field specifies the Virtual IP (VIP) address
   associated with the particular cluster.  This field is used for
   troubleshooting misconfigured routers.

   The VIP should be an IP address assigned from the subnet that the
   interface is attached.

5.3.9  Authentication Data

   The authentication string is currently utilized for simple text
   authentication, similar to the simple text authentication found in
   OSPF.  It is up to 8 characters of plain text.  If the configured
   authentication string is shorter than 8 bytes, the remaining space
   MUST be zero-filled. Any VRRP packet with an authentication string
   that does not match its configured authentication string should be
   discarded. The authentication string is unique on a per cluster
   basis.

6.  Protocol State Machine

6.1 Parameters


    Cluster_ID              Cluster identifier.  Configured item.

    Priority                Priority value for this cluster.  Configured
                            item.  Default is 100 (decimal).

    Virtual_IP              Virtual IP Address for this cluster.
                            Configured item.

    Advertisement_Interval  Time interval for Master to Send
                            ADVERTISEMENTS.  Default is 1 second.

    Skew_Time               Calculated time to skew
                            Master_Down_Interval.  Defined to be:

                               ( (256 - Priority) / 256 )







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    Master_Down_Interval    Time interval for Backup to declare Master
                            down.  Defined to be:

                               (3 * Advertisement_Interval) + Skew_time

                            seconds.


6.2 Timers

    Master_Down_Timer       Timer which fires when Master has not been
                            heard for Master_Down_Interval.

    Adver_Timer             Timer which fires when time to send next
                            ADVERTISEMENT based on
                            Advertisement_Interval.



6.3  State Transition Diagram

                          +---------------+
                          |               |<-------------+
               +--------->|  Initialize   |              |
               |          |               |----------+   |
               |          +---------------+          |   |
               |                                     |   |
               |                                     V   |
       +---------------+                       +---------------+
       |               |---------------------->|               |
       |    Master     |                       |    Backup     |
       |               |<----------------------|               |
       +---------------+                       +---------------+

6.4  State Descriptions

   In the below state descriptions, the state names will be identified
   as follows {state-name}, and the packets will be identified by
   utilizing all upper case characters.

6.4.1   Initialize

   {Initialize} is the initial state an interface takes when VRRP is
   enabled or disabled.  The basic function of the state is to wait for
   a startup event.  When that is received it:

      - Set the Master_Down_Timer to Master_Down_Interval




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      - Set state to {Backup} state.

6.4.2   Backup

   The main purpose of {Backup} state is for an interface to wait for
   the current master to stop sending ADVERTISEMENT packets.

   While in this state, an interface should do the following:

      - Should not respond to ARP request for the interface VIP router
         address

      - Should discard packets with destination link layer MAC address
         equal to virtual router MAC.

      - Should discard packets addressed to the interface VIP address.

      - If Master_Down_Timer fires, Send ADVERTISEMENT, set Adver_Timer
         to Advertisement_Interval, and set state to {Master} state

      - If ADVERTISEMENT received,

            If Priority of the received ADVERTISEMENT is Zero, then set
            Mater_Down_Timer to Skew_Time.

            If Priority of the received ADVERTISEMENT is greater than
            this interfaces Priority, then reset Master_Down_Timer.

            If Priority of the received ADVERTISEMENT is equal to this
            interfaces Priority, then reset Master_Down_Timer.

            If Priority of the received ADVERTISEMENT is lower than this
            interfaces Priority, then discard ADVERTISEMENT.

6.4.3   Master

   In {Master} state an interface is functioning as the actual physical
   router for the virtual router IP and MAC address.

   While in this state, an interface should do the following:

   - Accept and forward traffic for the virtual router MAC address.

   - Respond to ARP requests for the VIP address with the virtual router
      MAC address.

   - Respond to packets addressed to the VIP address.




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   - If Adver_Timer fires, send a ADVERTISEMENT and reset Adver_Timer.

   - If ADVERTISEMENT received,

         If Priority of the received ADVERTISEMENT is higher than this
         interfaces Priority, then cancel Adver_Timer, Set
         Master_Down_Timer, and set state to {Backup}.

         If Priority of the received ADVERTISEMENT is equal to this
         interfaces Priority, then:

            If IP Address of sender of ADVERTISEMENT is higher than this
            interfaces IP Address, then cancel Adver_Timer, Set
            Master_Down_Timer, and set state to {Backup}.

            If IP Address of sender of ADVERTISEMENT is lower than this
            interfaces IP Address, discard ADVERTISEMENT.

         If Priority of the received ADVERTISEMENT is lower than this
         interfaces Priority, discard ADVERTISEMENT.


6.5  State Table

   +---------------+---------------+---------------+---------------+
   |Current State->| {Initialize}  |   {Backup}    |   {Master}    |
   |               |               |               |               |
   |    Event      |               |               |               |
   |      |        |               |               |               |
   |      V        |               |               |               |
   +---------------+---------------+---------------+---------------+
   |               | Set Master_   |               |               |
   | Startup       |  Down_Timer   |               |               |
   |               | State =       |               |               |
   |               |  Backup       |               |               |
   +---------------+---------------+---------------+---------------+
   |               |               | Cancel Master_| Cancel Adver_ |
   | Shutdown      | Ignore        |  Down_Timer   |  Timer        |
   |               | Event         | State =       | Send ADVER w/ |
   |               |               |  Initialize   |  Priority=0   |
   |               |               |               | State = Init. |
   +---------------+---------------+---------------+---------------+
   |               |               | Send          |               |
   | Master_Down_  |               |  ADVERTISEMENT|               |
   | Timer fires   |               | Set Adver_    |               |
   |               |               |  Timer        |               |
   |               |               | State = Master|               |




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   +---------------+---------------+---------------+---------------+
   | Adver_Timer   |               |               | Send ADVER.   |
   | fires         |               |               | Reset Adver_  |
   |               |               |               |  Timer        |
   +---------------+---------------+---------------+---------------+
   | Receive VRRP  |               | Set Master_   | Send ADVER.   |
   | ADVERTISEMENT |               |  Down_Timer=  | Reset Adver_  |
   | with Priority |               | Skew_Timer    |  Timer        |
   | equal Zero    |               |               |               |
   +---------------+---------------+---------------+---------------+
   | Receive VRRP  |               |               | Cancel Adver_ |
   | ADVERTISEMENT |               | Reset         |  Timer        |
   | with Higher   |               | Master_Down_  | Set Master__  |
   | Priority      |               | Timer         |  Down_Timer   |
   |               |               |               | State = Backup|
   +---------------+---------------+---------------+---------------+
   | Receive VRRP  |               |               | Cancel Adver_ |
   | ADVERTISEMENT |               | Reset         |  Timer        |
   | with Equal    |               | Master_Down_  | Set Master__  |
   | Priority      |               | Timer         |  Down_Timer   |
   | and Higher IP |               |               | State = Backup|
   | Address       |               |               |               |
   +---------------+---------------+---------------+---------------+
   | Receive VRRP  |               |               |               |
   | ADVERTISEMENT |               | Reset         |  Discard      |
   | with Equal    |               | Master_Down   |  Packet       |
   | Priority      |               | Timer         |               |
   | and Lower IP  |               |               |               |
   | Address       |               |               |               |
   +---------------+---------------+---------------+---------------+
   | Receive VRRP  |               |               |               |
   | ADVERTISEMENT |               | Discard       |  Discard      |
   | with Lower    |               | Packet        |  Packet       |
   | Priority      |               |               |               |
   +---------------+---------------+---------------+---------------+
   | Receive ARP   |               |               |  Send ARP     |
   | Request for   |               | Discard       |  Reply w/     |
   | VIP address   |               | Packet        |  VMAC         |
   +---------------+---------------+---------------+---------------+
   | Receive IP    |               |               |  Process as   |
   | packet w/     |               |               |  Normal IP    |
   | Destination   |               |               |  Packet sent  |
   | = VIP         |               |               |  to Router    |
   +---------------+---------------+---------------+---------------+
   | Receive IP    |               |               |  Process and  |
   | packet w/     |               |               |  Forward as   |
   | Dest. MAC     |               |               |  Normal IP    |
   | = VMAC        |               |               |  Packet       |



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   +---------------+---------------+---------------+---------------+
   | Unknown VRRP  |               | Discard       |  Discard      |
   | packet        |               | Packet        |  Packet       |
   +---------------+---------------+---------------+---------------+


7.  Sending and Receiving VRRP Packets


7.1  Receiving VRRP Packets

   The following rules must be performed when a VRRP packet is received:

      - Verify TTL = 255.
      - Verify that received packet length is greater or equal to VRRP
        header length.
      - Verify checksum in packet
      - Verify version
      - Verify Source address does not equal interface IP address
      - Verify Cluster identifier valid on received interface
      - Perform indicated authentication
      - Verify VIP in packet is same as configured VIP for this cluster
      - Verify Adver Interval in packet is same as configured VIP for
        this cluster

   If one of these checks fails, the receiver should discard the packet,
   log the event and indicate via network management that an error
   occurred.


7.2 Transmitting Packets

   The following operations must be performed prior to transmitting a
   VRRP packet.

      - Fill in packet fields with appropriate interface and cluster
        information
      - Compute Checksum
      - Set source MAC to Virtual MAC Address
      - Send to VRRP IP Multicast Group

   Note: VRRP packets are transmitted with the Virtual MAC address as
   the source MAC to ensure that learning bridges correctly determine
   the LAN segment the virtual MAC is attached to.







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7.3 Virtual MAC Address

   The default virtual MAC address associated with the virtual IP
   address is a IEEE 802 MAC Address of the following format:

   00-00-5E-XX-XX-{cluster id} (in hex in internet standard bit-order)

   The first three octets are the IANA's OUI.  The next two octets (to
   be assigned by the IANA) indicate the address address block assigned
   to the VRRP protocol.  {cluster id} in the last octet is the VRRP
   cluster identifier.  This mapping allows for up to 255 VRRP clusters
   per interface.

   Implementations may also allow Virtual MAC addresses to be configured
   for each cluster.


8.  Host Operation

8.1  Host ARP Requests

   When a client sends a ARP request for the virtual IP address, the
   appropriate master router should respond to the ARP request with the
   above virtual MAC address for the appropriate cluster.  This allows
   the client to always use the same MAC address regardless of the
   current master router.  The request should be handled as a standard
   ARP reply.


9.  Operational Issues

9.1 ICMP Redirects

   VRRP operation relies on the client host only using the Virtual IP
   address and corresponding Virutal MAC.  It is important that client
   hosts do not learn the real IP address of VRRP routers on LAN
   segment.  Consequentially routers on the same LAN segment MUST NOT
   send ICMP Redirects with the real IP address of any VRRP routers.


9.2 Proxy ARP

   If Proxy ARP is being used on routers running VRRP, the VRRP routers
   must advertise the Virtual MAC address in the Proxy ARP message.
   Doing otherwise would cause them to learn the real IP address of the
   VRRP routers.





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9.3 Network Management

   It is important that network management tools (e.g., SNMP, Telnet,
   etc.)  always use the real IP addresses of VRRP routers.  This is
   necessary to insure that network management is aware of the real
   status of the VRRP routers (e.g., detect that a router has failed so
   that it can be repaired).


10.  Operation over Token Ring

   TBD







































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11.  References

   [AUTH]    Atkinson, R., "IP Authentication Header", RFC 1826, Naval
             Research Laboratory, August 1995.

   [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
             Requirement Levels", RFC2119, BCP14, March 1997.

12. Security Considerations

   The protocol design supports no authentication, simple text
   authentication, and integrity/authentication/integrity using the IP
   Security options.

13. Author's Addresses

   Steven Knight                           Phone: +1 612 943-8990
   Ascend Communications                   EMail: Steven.Knight@ascend.com
   High Performance Network Division
   10250 Valley View Road, Suite 113
   Eden Prairie, MN USA 55344

   Douglas Weaver                          Phone: +1 612 943-8990
   Ascend Communications                   EMail: Doug.Weaver@ascend.com
   High Performance Network Division
   10250 Valley View Road, Suite 113
   Eden Prairie, MN USA 55344

   David Whipple                           Phone: +1 206 703-3876
   Microsoft Corporation                   EMail: dwhipple@microsoft.com
   One Microsoft Way
   Redmond, WA USA 98052-6399

   Robert Hinden                           Phone: +1 408 990-2004
   Ipsilon Networks, Inc.                  EMail: hinden@ipsilon.com
   232 Java Drive
   Sunnyvale, CA 94089

14. Acknowledgments

   The authors would like to thank Glen Zorn, and Michael Lane, Clark
   Bremer, Hal Peterson, Danny Mitzel, and Peter Hunt for their comments
   and suggestions.








draft-ietf-vrrp-spec-00.txt                                    [Page 17]


INTERNET-DRAFT     Virtual Router Redundancy Protocol       22 June 1997


15. Changes from Previous Drafts

   Changes from <draft-hinden-vrrp-00.txt>

    - Changed default behavior to stay with current master when
      priorities are equal.  This behavior can be changed by configuring
      explicit priorities.

    - Changed Master state behavior to not send Advertisements when
      receiving Advertisement with lower priorty.  Change reduces worst
      case election message overhead to "n", where "n" is number of
      configured equal priority VRRP routers.

    - Added Skew_Time parameter and changed receiving advertisement with
      zero priority behavior to cause resulting advertisement sent to be
      skewed by priority.

    - Changed sending behavior to send VRRP packets with VMAC as source
      MAC and added text describing why this is important for bridged
      environments.

    - Changed definition of VMAC to be in IANA assigned unicast MAC
      block.

    - Added Advertisement Interval to VRRP header.

    - Added text regarding ICMP Redirects, Proxy ARP, and network
      management issues.

    - Various small text clarifications.





















draft-ietf-vrrp-spec-00.txt                                    [Page 18]


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