HSRP election question

jason_lunde

Just a quick one. Supposedly if two devices are configured for HSRP and they have the same priority (say the default of 100), then the device with the higher IP address on the assigned HSRP interface will become active. (I took this from page 318 of the BCMSN off. exam cert guide). I labbed this up, and did not quite have these results. I assigned one physical ip of 192.168.1.3 and another of 192.168.1.66 (both with an hsrp addy of 192.168.1.1). I left the priorities the default, and enabled preempt. The first interface to come up was active...the higher ip, 192.168.1.66, never just took over because it had the higher ip. It was always the interface that came up first (if that makes sense). I enabled debugging for standby, and never really saw anything conclusive.

Typing this I tried something though...I shut both vlan interfaces, and did a no shut almost simultaneously (actually hit no shut on the lower IP'd interface a split second faster)...
The higher interface IP device did win the election. I guess if you "force" an election this will happen correctly. You have to bring them up in a way that the election does actually take place. Otherwise the first device to come up will just assume the active role, and without a higher priority, another device cannot take over until a failure. Interesting.

SysAdmin4066

That's very interesting, I'll have to try that out.

base2

i wonder what would change if you tried to add the pre-empt command in there.

SysAdmin4066

Says he enabled preempt.

jason_lunde

ya, I had indeed enabled preempt before I started the testing.

BennyLava

A higher IP won't preempt in HSRP, only a higher priority will. VRRP is the only one of the 3 first hop redundancy protocols where a higher IP will preempt.

jason_lunde

BennyLava wrote: »

A higher IP won't preempt in HSRP, only a higher priority will. VRRP is the only one of the 3 first hop redundancy protocols where a higher IP will preempt.

Good to know Benny, Thanks!