HSRP default behavior

[ravindra Krishna]

Hi All,

The default behavior of HSRP(with Priorities to default) should make the router active if it has highest interface IP address. But it is not happening practically (note that R1 with IP 192.168.10.2 has been configured first)

R2(config)#interface vlan 10

R2(config-if)#ip add 192

*Mar  1 00:04:42.979: %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan10, changed state to up

R2(config-if)#ip add 192.168.10.3 255.255.255.0

R2(config-if)#st

R2(config-if)#standby 10 ip 192.168.10.1

R2(config-if)#do ping 192.168.10.2

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 192.168.10.2, timeout is 2 seconds:

.!!!!

Success rate is 80 percent (4/5), round-trip min/avg/max = 12/31/48 ms

R2(config-if)#exit

R2(config)#

*Mar  1 00:05:32.727: %HSRP-5-STATECHANGE: Vlan10 Grp 10 state Speak -> Standby

R2(config)#do show standby

Vlan10 - Group 10

  State is Standby

    1 state change, last state change 00:00:24

  Virtual IP address is 192.168.10.1

  Active virtual MAC address is 0000.0c07.ac0a

    Local virtual MAC address is 0000.0c07.ac0a (v1 default)

  Hello time 3 sec, hold time 10 sec

    Next hello sent in 2.808 secs

  Preemption disabled

  Active router is 192.168.10.2, priority 100 (expires in 7.360 sec)

  Standby router is local

  Priority 100 (default 100)

  IP redundancy name is "hsrp-Vl10-10" (default)

Any reason for this behavior? Please let me know if I am wrong.

Regards,

Ravi

[Amit Singh]

Ravi,

That highest IP address for the HSRP active comes into the picture when both the routers reboot at the same time and the HSRP elect starts happening. If a router is already configured with the HSRP IP and you configure another router with the HSRP, it wont force the active router to go to HSRP standby state.

http://www.cisco.com/en/US/tech/tk648/tk362/technologies_tech_note09186a0080094a91.shtml

Hope this helps.

Cheers,

-amit singh

[krahmani323]

Hello Ravi, Hello Amit,

As per discussion

https://supportforums.cisco.com/message/3520251#3520251

And even if you configure preemption the routers, this behaviour is the expected one as documented by bug CSCdv91652 - HSRP should not preempt if priorities are equal

Before in earlier versions it should have preempted, but the behaviour has been changed since. 

http://tools.cisco.com/Support/BugToolKit/search/getBugDetails.do?method=fetchBugDetails&bugId=CSCdv91652

This ddts is an enhancement to the HSRP preempt mechanism.

An Active HSRP router may be preempted by an equal priority non-Active router if the non-Active router has a numerically greater interface IP address.

This is the current expected behaviour, since the interface IP address is used as a tie-breaker in situations where the prioritues are equal.

This ddts changes that behaviour such that an equal priority non-Active router will never preempt the current Active router.

Kind regards.

Karim