HSRP Version 2

2017-11-03 09:05:05

Problem

You want to implement HSRP Version 2.

Solution

To enable HSRP Version 2, use the standby version 2 configuration command:

Router1#configure terminal Enter configuration commands, one per line. End with CNTL/Z. Router1(config)#interface FastEthernet0/1 Router1(config-if)#standby version 2 Router1(config-if)#standby 4095 ip 10.1.1.1 Router1(config-if)#standby 4095 timers msec 15 msec 50 Router1(config-if)#standby 4095 priority 200 Router1(config-if)#standby 4095 preempt Router1(config-if)#end Router1#

You must also configure every router that participates in the same HSRP group with the same version number:

Router2#configure terminal Enter configuration commands, one per line. End with CNTL/Z. Router2(config)#interface FastEthernet0/0 Router2(config-if)#standby version 2 Router2(config-if)#standby 4095 ip 10.1.1.1 Router2(config-if)#standby 4095 timers msec 15 msec 50 Router2(config-if)#standby 4095 priority 150 Router2(config-if)#standby 4095 preempt Router2(config-if)#end Router2#

Cisco added support for HSRP Version 2, beginning with IOS Version 12.3(4)T.

Discussion

Fortunately, all of the HSRP commands remain the same from Version 1, with one noticeable difference, the expanded HSRP group numbering range. As you recall from Recipe 22.1, HSRP Version 1 only supported 256 groups ranging from 0 to 255. One of the enhancements of HSRP Version 2 is the expanded group numbering, which ranges from 0 to 4,095. This enhancement allows you to match HSRP group numbers to VLAN numbers on Subinterfaces.

With the exception of the expanded HSRP group numbering, all of the previous HSRP commands remain valid. In fact, the router will default to HSRP Version 1 unless you explicitly configure the router to use Version 2. To upgrade to HSRP Version 2 you need only implement a single command, standby version 2.

HSRP Version 1 and Version 2 are not interoperable. You cannot run both HSRP versions on a single interface; however, you can run different versions on different physical interfaces within the same router.

Also, since HSRP Version 1 and Version 2 use completely different virtual MAC addresses and IP multicast addresses, they will not communicate with one another, even if configured to use the same HSRP group number on the same network segment.

To view the current HSRP configuration, use the show standby command:

Router1#show standby FastEthernet0/1 - Group 4095 (version 2) State is Active 2 state changes, last state change 00:11:47 Virtual IP address is 10.1.1.1 Active virtual MAC address is 0000.0c9f.ffff Local virtual MAC address is 0000.0c9f.ffff (v2 default) Hello time 15 msec, hold time 50 msec Next hello sent in 0.007 secs Preemption enabled Active router is local Standby router is 10.1.1.3, priority 150 (expires in 0.030 sec) Priority 200 (configured 200) IP redundancy name is "hsrp-Fa0/1-4095" (default) Router1#

Notice that Router1 is configured to use HSRP Version 2 as highlighted, and also notice the HSRP Version 2 virtual MAC address of 0000.0c9f.ffff.

We note in passing that although you can readily change from Version 1 to Version 2, you won't be permitted to change from Version 2 to Version 1 if you use one of the expanded group numbers. Since Version 1 only supports up to group number 255, the router will not permit you to change the version number if the group number exceeds 255. In the following example, we attempt to change back to Version 1; however, the router has been configured to use group 4,095:

Router1#configure terminal Enter configuration commands, one per line. End with CNTL/Z. Router1(config)#standby version 1 ^ % Invalid input detected at '^' marker. Router1(config)#end Router1#

See the introduction of this chapter for more information about HSRP Version 2.

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