draft-ietf-vrrp-spec-v2-02.txt   draft-ietf-vrrp-spec-v2-03.txt 
INTERNET-DRAFT S. Knight INTERNET-DRAFT S. Knight
May 28, 1999 D. Weaver June 17, 1999 D. Weaver
Ascend Communications, Inc. Ascend Communications, Inc.
D. Whipple D. Whipple
Microsoft, Inc. Microsoft, Inc.
R. Hinden R. Hinden
D. Mitzel D. Mitzel
P. Hunt P. Hunt
Nokia Nokia
P. Higginson P. Higginson
M. Shand M. Shand
Digital Equipment Corp. Digital Equipment Corp.
A. Lindem A. Lindem
IBM Corporation IBM Corporation
Virtual Router Redundancy Protocol Virtual Router Redundancy Protocol
<draft-ietf-vrrp-spec-v2-02.txt> <draft-ietf-vrrp-spec-v2-03.txt>
Status of this Memo Status of this Memo
This document is an Internet-Draft and is in full conformance with This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of [RFC2026]. all provisions of Section 10 of [RFC2026].
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet- other groups may also distribute working documents as Internet-
Drafts. Drafts.
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and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt http://www.ietf.org/ietf/1id-abstracts.txt
The list of Internet-Draft Shadow Directories can be accessed at The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html. http://www.ietf.org/shadow.html.
This internet draft expires on November 28, 1999. This internet draft expires on December 17, 1999.
Abstract Abstract
This memo defines the Virtual Router Redundancy Protocol (VRRP). This memo defines the Virtual Router Redundancy Protocol (VRRP).
VRRP specifies an election protocol that dynamically assigns VRRP specifies an election protocol that dynamically assigns
responsibility for a virtual router to one of the VRRP routers on a responsibility for a virtual router to one of the VRRP routers on a
LAN. The VRRP router controlling the IP address(es) associated with LAN. The VRRP router controlling the IP address(es) associated with
a virtual router is called the Master, and forwards packets sent to a virtual router is called the Master, and forwards packets sent to
these IP addresses. The election process provides dynamic fail over these IP addresses. The election process provides dynamic fail over
in the forwarding responsibility should the Master become in the forwarding responsibility should the Master become
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advantage gained from using VRRP is a higher availability default advantage gained from using VRRP is a higher availability default
path without requiring configuration of dynamic routing or router path without requiring configuration of dynamic routing or router
discovery protocols on every end-host. discovery protocols on every end-host.
Table of Contents Table of Contents
1. Introduction...............................................3 1. Introduction...............................................3
2. Required Features..........................................5 2. Required Features..........................................5
3. VRRP Overview..............................................7 3. VRRP Overview..............................................7
4. Sample Configurations......................................8 4. Sample Configurations......................................8
5. Protocol..................................................10 5. Protocol..................................................11
5.1 VRRP Packet Format....................................10 5.1 VRRP Packet Format....................................11
5.2 IP Field Descriptions.................................11 5.2 IP Field Descriptions.................................11
5.3 VRRP Field Descriptions...............................11 5.3 VRRP Field Descriptions...............................12
6. Protocol State Machine....................................14 6. Protocol State Machine....................................15
6.1 Parameters per Virtual Router.........................14 6.1 Parameters per Virtual Router.........................15
6.2 Timers................................................15 6.2 Timers................................................16
6.3 State Transition Diagram..............................16 6.3 State Transition Diagram..............................16
6.4 State Descriptions....................................16 6.4 State Descriptions....................................16
7. Sending and Receiving VRRP Packets........................19 7. Sending and Receiving VRRP Packets........................20
7.1 Receiving VRRP Packets................................19 7.1 Receiving VRRP Packets................................20
7.2 Transmitting Packets..................................20 7.2 Transmitting Packets..................................20
7.3 Virtual MAC Address...................................20 7.3 Virtual MAC Address...................................21
8. Operational Issues........................................21 8. Operational Issues........................................22
8.1 ICMP Redirects........................................21 8.1 ICMP Redirects........................................22
8.2 Host ARP Requests.....................................21 8.2 Host ARP Requests.....................................22
8.3 Proxy ARP.............................................21 8.3 Proxy ARP.............................................22
8.4 Potential Forwarding Loop.............................22 8.4 Potential Forwarding Loop.............................23
9. Operation over FDDI, Token Ring, and ATM LANE.............22 9. Operation over FDDI, Token Ring, and ATM LANE.............23
9.1 Operation over FDDI...................................22 9.1 Operation over FDDI...................................23
9.2 Operation over Token Ring.............................22 9.2 Operation over Token Ring.............................23
9.3 Operation over ATM LANE...............................24 9.3 Operation over ATM LANE...............................25
10. Security Considerations...................................25 10. Security Considerations...................................26
10.1 No Authentication....................................25 10.1 No Authentication....................................26
10.2 Simple Text Password.................................25 10.2 Simple Text Password.................................26
10.3 IP Authentication Header.............................26 10.3 IP Authentication Header.............................27
11. Acknowledgments...........................................27 11. Acknowledgments...........................................28
12. References................................................27 12. References................................................28
13. Authors' Addresses........................................28 13. Authors' Addresses........................................29
14. Changes from RFC2338......................................30 14. Changes from RFC2338......................................31
1. Introduction 1. Introduction
There are a number of methods that an end-host can use to determine There are a number of methods that an end-host can use to determine
its first hop router towards a particular IP destination. These its first hop router towards a particular IP destination. These
include running (or snooping) a dynamic routing protocol such as include running (or snooping) a dynamic routing protocol such as
Routing Information Protocol [RIP] or OSPF version 2 [OSPF], running Routing Information Protocol [RIP] or OSPF version 2 [OSPF], running
an ICMP router discovery client [DISC] or using a statically an ICMP router discovery client [DISC] or using a statically
configured default route. configured default route.
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4. Sample Configurations 4. Sample Configurations
4.1 Sample Configuration 1 4.1 Sample Configuration 1
The following figure shows a simple network with two VRRP routers The following figure shows a simple network with two VRRP routers
implementing one virtual router. Note that this example is provided implementing one virtual router. Note that this example is provided
to help understand the protocol, but is not expected to occur in to help understand the protocol, but is not expected to occur in
actual practice. actual practice.
+-----+ +-----+ +-----------+ +-----------+
| MR1 | | BR1 | | Rtr1 | | Rtr2 |
| | | | |(MR VRID=1)| |(BR VRID=1)|
| | | | | | | |
VRID=1 +-----+ +-----+ VRID=1 +-----------+ +-----------+
IP A ---------->* *<--------- IP B IP A ---------->* *<--------- IP B
| | | |
| | | |
| |
------------------+------------+-----+--------+--------+--------+-- ------------------+------------+-----+--------+--------+--------+--
^ ^ ^ ^ ^ ^ ^ ^
| | | | | | | |
(IP A) (IP A) (IP A) (IP A) (IP A) (IP A) (IP A) (IP A)
| | | | | | | |
+--+--+ +--+--+ +--+--+ +--+--+ +--+--+ +--+--+ +--+--+ +--+--+
| H1 | | H2 | | H3 | | H4 | | H1 | | H2 | | H3 | | H4 |
+-----+ +-----+ +--+--+ +--+--+ +-----+ +-----+ +--+--+ +--+--+
Legend: Legend:
---+---+---+-- = Ethernet, Token Ring, or FDDI ---+---+---+-- = Ethernet, Token Ring, or FDDI
H = Host computer H = Host computer
MR = Master Router MR = Master Router
BR = Backup Router BR = Backup Router
* = IP Address * = IP Address
(IP) = default router for hosts (IP) = default router for hosts
Eliminating all mention of VRRP (VRID=1) from the figure above leaves
it as a typical IP deployment. Each router is permanently assigned
an IP address on the LAN interface (Rtr1 is assigned IP A and Rtr2 is
assigned IP B), and each host installs a static default route through
one of the routers (in this example they all use Rtr1's IP A).
The above configuration shows a very simple VRRP scenario. In this Moving to the VRRP environment, each router has the exact same
configuration, the end-hosts install a default route to the IP permanently assigned IP address. Rtr1 is said to be the IP address
address of virtual router #1 (IP A) and both routers run VRRP. The owner of IP A, and Rtr2 is the IP address owner of IP B. A virtual
router on the left becomes the Master for virtual router #1 (VRID=1) router is then defined by associating a unique identifier (the
and the router on the right is the Backup for virtual router #1. If virtual router ID) with the address owned by a router. Finally, the
the router on the left should fail, the other router will take over VRRP protocol manages virtual router failover to a backup router.
virtual router #1 and its IP addresses, and provide uninterrupted
service for the hosts.
Note that in this example, IP B is not backed up by the router on the The example above shows a virtual router configured to cover the IP
left. IP B is only used by the router on the right as its interface address owned by Rtr1 (VRID=1,IP_Address=A). When VRRP is enabled on
address. In order to backup IP B, a second virtual router would have Rtr1 for VRID=1 it will assert itself as Master, with priority=255,
to be configured. This is shown in the next section. since it is the IP address owner for the virtual router IP address.
When VRRP is enabled on Rtr2 for VRID=1 it will transition to Backup,
with priority=100, since it is not the IP address owner. If Rtr1
should fail then the VRRP protocol will transition Rtr2 to Master,
temporarily taking over forwarding responsibility for IP A to provide
uninterrupted service to the hosts.
Note that in this example IP B is not backed up, it is only used by
Rtr2 as its interface address. In order to backup IP B, a second
virtual router must be configured. This is shown in the next
section.
4.2 Sample Configuration 2 4.2 Sample Configuration 2
The following figure shows a configuration with two virtual routers The following figure shows a configuration with two virtual routers
with the hosts spitting their traffic between them. This example is with the hosts spitting their traffic between them. This example is
expected to be very common in actual practice. expected to be very common in actual practice.
+-----+ +-----+ +-----------+ +-----------+
| MR1 | | MR2 | | Rtr1 | | Rtr2 |
| & | | & | |(MR VRID=1)| |(BR VRID=1)|
| BR2 | | BR1 | |(BR VRID=2)| |(MR VRID=2)|
VRID=1 +-----+ +-----+ VRID=2 VRID=1 +-----------+ +-----------+ VRID=2
IP A ---------->* *<---------- IP B IP A ---------->* *<---------- IP B
| | | |
| | | |
| |
------------------+------------+-----+--------+--------+--------+-- ------------------+------------+-----+--------+--------+--------+--
^ ^ ^ ^ ^ ^ ^ ^
| | | | | | | |
(IP A) (IP A) (IP B) (IP B) (IP A) (IP A) (IP B) (IP B)
| | | | | | | |
+--+--+ +--+--+ +--+--+ +--+--+ +--+--+ +--+--+ +--+--+ +--+--+
| H1 | | H2 | | H3 | | H4 | | H1 | | H2 | | H3 | | H4 |
+-----+ +-----+ +--+--+ +--+--+ +-----+ +-----+ +--+--+ +--+--+
Legend: Legend:
---+---+---+-- = Ethernet, Token Ring, or FDDI ---+---+---+-- = Ethernet, Token Ring, or FDDI
H = Host computer H = Host computer
MR = Master Router MR = Master Router
BR = Backup Router BR = Backup Router
* = IP Address * = IP Address
(IP) = default router for hosts (IP) = default router for hosts
In the above configuration, half of the hosts install a default route In the example above, half of the hosts have configured a static
to virtual router #1's IP address (IP A), and the other half of the route through Rtr1's IP A and half are using Rtr2's IP B. The
hosts install a default route to virtual router #2's IP address (IP configuration of virtual router VRID=1 is exactly the same as in the
B). This has the effect of load balancing the outgoing traffic, first example (see section 4.1), and a second virtual router has been
while also providing full redundancy. added to cover the IP address owned by Rtr2 (VRID=2, IP_Address=B).
In this case Rtr2 will assert itself as Master for VRID=2 while Rtr1
will act as a backup. This scenario demonstrates a deployment
providing load splitting when both routers are available while
providing full redundancy for robustness.
5.0 Protocol 5.0 Protocol
The purpose of the VRRP packet is to communicate to all VRRP routers The purpose of the VRRP packet is to communicate to all VRRP routers
the priority and the state of the Master router associated with the the priority and the state of the Master router associated with the
Virtual Router ID. Virtual Router ID.
VRRP packets are sent encapsulated in IP packets. They are sent to VRRP packets are sent encapsulated in IP packets. They are sent to
the IPv4 multicast address assigned to VRRP. the IPv4 multicast address assigned to VRRP.
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endif endif
endif endif
7. Sending and Receiving VRRP Packets 7. Sending and Receiving VRRP Packets
7.1 Receiving VRRP Packets 7.1 Receiving VRRP Packets
Performed the following functions when a VRRP packet is received: Performed the following functions when a VRRP packet is received:
- MUST verify that the IP TTL is 255. - MUST verify that the IP TTL is 255.
- MUST verify the VRRP version - MUST verify the VRRP version is 2
- MUST verify that the received packet contains the complete VRRP - MUST verify that the received packet contains the complete VRRP
packet (including fixed fields, IP Address(es), and packet (including fixed fields, IP Address(es), and
Authentication Data). Authentication Data).
- MUST verify the VRRP checksum - MUST verify the VRRP checksum
- MUST verify that the VRID is configured on the receiving - MUST verify that the VRID is configured on the receiving
interface and the local router is not the IP Address owner interface and the local router is not the IP Address owner
(Priority equals 255 (decimal)). (Priority equals 255 (decimal)).
- MUST verify that the Auth Type matches the locally configured - MUST verify that the Auth Type matches the locally configured
authentication method for the virtual router and perform that authentication method for the virtual router and perform that
authentication method authentication method
If any one of the above checks fails, the receiver MUST discard the If any one of the above checks fails, the receiver MUST discard the
packet, SHOULD log the event and MAY indicate via network management packet, SHOULD log the event and MAY indicate via network management
that an error occurred. that an error occurred.
- MAY verify that the IP address(es) associated with the VRID are - MAY verify that "Count IP Addrs" and the list of IP Address
valid matches the IP_Addresses configured for the VRID
If the above check fails, the receiver SHOULD log the event and MAY If the above check fails, the receiver SHOULD log the event and MAY
indicate via network management that a misconfiguration was detected. indicate via network management that a misconfiguration was detected.
If the packet was not generated by the address owner (Priority does If the packet was not generated by the address owner (Priority does
not equal 255 (decimal)), the receiver MUST drop the packet, not equal 255 (decimal)), the receiver MUST drop the packet,
otherwise continue processing. otherwise continue processing.
- MUST verify that the Adver Interval in the packet is the same as - MUST verify that the Adver Interval in the packet is the same as
the locally configured for this virtual router the locally configured for this virtual router
If the above check fails, the receiver MUST discard the packet, If the above check fails, the receiver MUST discard the packet,
skipping to change at page 22, line 9 skipping to change at page 23, line 9
8.3 Proxy ARP 8.3 Proxy ARP
If Proxy ARP is to be used on a VRRP router, then the VRRP router If Proxy ARP is to be used on a VRRP router, then the VRRP router
must advertise the Virtual Router MAC address in the Proxy ARP must advertise the Virtual Router MAC address in the Proxy ARP
message. Doing otherwise could cause hosts to learn the real MAC message. Doing otherwise could cause hosts to learn the real MAC
address of the VRRP router. address of the VRRP router.
8.4 Potential Forwarding Loop 8.4 Potential Forwarding Loop
When a VRRP router assumes forwarding responsibility for IP A VRRP router SHOULD not forward packets addressed to the IP
address(es) it is not the owner, it SHOULD not forward packets Address(es) it becomes Master for if it is not the owner. Forwarding
addressed to the IP address(es). This would result in unnecessary these packets would result in unnecessary traffic. Also in the case
traffic and in the case of LANs that receive packets they transmit of LANs that receive packets they transmit (e.g., token ring) this
(e.g., token ring) this can result in a forwarding loop that is only can result in a forwarding loop that is only terminated when the IP
terminated when the IP TTL expires. TTL expires.
One such mechanism for VRRP routers is to add/delete a reject host One such mechanism for VRRP routers is to add/delete a reject host
route for each adopted IP address when transitioning to/from MASTER route for each adopted IP address when transitioning to/from MASTER
state. state.
9. Operation over FDDI, Token Ring, and ATM LANE 9. Operation over FDDI, Token Ring, and ATM LANE
9.1 Operation over FDDI 9.1 Operation over FDDI
FDDI interfaces remove from the FDDI ring frames that have a source FDDI interfaces remove from the FDDI ring frames that have a source
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control over the administration of nodes on a LAN. While this type control over the administration of nodes on a LAN. While this type
of authentication does protect the operation of VRRP, there are other of authentication does protect the operation of VRRP, there are other
types of attacks that may be employed on shared media links (e.g., types of attacks that may be employed on shared media links (e.g.,
generation of bogus ARP replies) that are independent from VRRP and generation of bogus ARP replies) that are independent from VRRP and
are not protected. are not protected.
11. Acknowledgments 11. Acknowledgments
The authors would like to thank Glen Zorn, and Michael Lane, Clark The authors would like to thank Glen Zorn, and Michael Lane, Clark
Bremer, Hal Peterson, Tony Li, Barbara Denny, Joel Halpern, Steve Bremer, Hal Peterson, Tony Li, Barbara Denny, Joel Halpern, Steve
Bellovin Thomas Narten, and Rob Montgomery for their comments and Bellovin, Thomas Narten, Rob Montgomery, and Rob Coltun for their
suggestions. comments and suggestions.
12. References 12. References
[802.1D] International Standard ISO/IEC 10038: 1993, ANSI/IEEE Std [802.1D] International Standard ISO/IEC 10038: 1993, ANSI/IEEE Std
802.1D, 1993 edition. 802.1D, 1993 edition.
[AUTH] Kent, S., R. Atkinson, "IP Authentication Header", RFC2402, [AUTH] Kent, S., R. Atkinson, "IP Authentication Header", RFC2402,
November 1998. November 1998.
[CKSM] Braden, R., D. Borman, C. Partridge, "Computing the [CKSM] Braden, R., D. Borman, C. Partridge, "Computing the
Internet Checksum", RFC1071, September 1988. Internet Checksum", RFC1071, September 1988.
[DISC] Deering, S., "ICMP Router Discovery Messages", RFC1256, [DISC] Deering, S., "ICMP Router Discovery Messages", RFC1256,
September 1991. September 1991.
[DHCP] Droms, R., "Dynamic Host Configuration Protocol", RFC1541, [DHCP] Droms, R., "Dynamic Host Configuration Protocol", RFC2131,
October 1993. March 1997.
[HMAC] Madson, C., R. Glenn, "The Use of HMAC-MD5-96 within ESP [HMAC] Madson, C., R. Glenn, "The Use of HMAC-MD5-96 within ESP
and AH", RFC2403, November 1998. and AH", RFC2403, November 1998.
[HSRP] Li, T., B. Cole, P. Morton, D. Li, "Cisco Hot Standby [HSRP] Li, T., B. Cole, P. Morton, D. Li, "Cisco Hot Standby
Router Protocol (HSRP)", RFC2281, March 1998. Router Protocol (HSRP)", RFC2281, March 1998.
[IPSTB] Higginson, P., M. Shand, "Development of Router Clusters to [IPSTB] Higginson, P., M. Shand, "Development of Router Clusters to
Provide Fast Failover in IP Networks", Digital Technical Provide Fast Failover in IP Networks", Digital Technical
Journal, Volume 9 Number 3, Winter 1997. Journal, Volume 9 Number 3, Winter 1997.
[IPX] Novell Incorporated., "IPX Router Specification", Version [IPX] Novell Incorporated., "IPX Router Specification", Version
1.10, October 1992. 1.10, October 1992.
[OSPF] Moy, J., "OSPF version 2", RFC1583, July 1997. [OSPF] Moy, J., "OSPF version 2", RFC2338, STD0054, April 1998.
[RIP] Hedrick, C., "Routing Information Protocol" , RFC1058, June [RIP] Malkin, G., "RIP Version 2", RFC2453, STD0056, November
1988. 1998.
[RFC1469] Pusateri, T., "IP over Token Ring LANs", RFC1469, June [RFC1469] Pusateri, T., "IP Multicast over Token Ring Local Area
1993. Networks", RFC1469, June 1993.
[RFC2026] Bradner, S., The Internet Standards Process -- Revision 3, [RFC2026] Bradner, S., "The Internet Standards Process -- Revision
RFC2026, October 1996. 3", RFC2026, BCP00009, October 1996.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", RFC2119, BCP14, March 1997. Requirement Levels", RFC2119, BCP0014, March 1997.
[TKARCH] IBM Token-Ring Network, Architecture Reference, Publication [TKARCH] IBM Token-Ring Network, Architecture Reference, Publication
SC30-3374-02, Third Edition, (September, 1989). SC30-3374-02, Third Edition, (September, 1989).
13. Author's Addresses 13. Author's Addresses
Steven Knight Phone: +1 612 943-8990 Steven Knight Phone: +1 612 943-8990
Ascend Communications EMail: Steven.Knight@ascend.com Ascend Communications EMail: Steven.Knight@ascend.com
High Performance Network Division High Performance Network Division
10250 Valley View Road, Suite 113 10250 Valley View Road, Suite 113
skipping to change at page 30, line 7 skipping to change at page 31, line 7
UK UK
Acee Lindem Phone: 1-919-254-1805 Acee Lindem Phone: 1-919-254-1805
IBM Corporation E-Mail: acee@raleigh.ibm.com IBM Corporation E-Mail: acee@raleigh.ibm.com
P.O. Box 12195 P.O. Box 12195
Research Triangle Park, NC 27709 Research Triangle Park, NC 27709
USA USA
14. Changes from RFC2338 14. Changes from RFC2338
- Revised the section 4 examples text with a clearer description of
mapping of IP address owner, priorities, etc.
- Clarify the section 7.1 text describing address list validation.
- Corrected text in Preempt_Mode definition. - Corrected text in Preempt_Mode definition.
- Changed authentication to be per Virtual Router instead of per - Changed authentication to be per Virtual Router instead of per
Interface. Interface.
- Added new subsection (9.3) stating that VRRP over ATM LANE is - Added new subsection (9.3) stating that VRRP over ATM LANE is
beyond the scope of this document. beyond the scope of this document.
- Clarified text describing received packet length check. - Clarified text describing received packet length check.
- Clarified text describing received authentication check. - Clarified text describing received authentication check.
- Clarified text describing VRID verification check. - Clarified text describing VRID verification check.
- Added new subsection (8.4) describing need to not forward packets - Added new subsection (8.4) describing need to not forward packets
for adopted IP addresses. for adopted IP addresses.
 End of changes. 

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