topic HSRP Preempt and tracking questions in Routing and SD-WAN

HSRP Preempt and tracking questions

Kevin Melton — Mon, 04 Mar 2019 00:47:39 GMT

I am going to be testing some HSRP configurations this evening for one of our Customers.

They have 2 2600 series routers facing the Internet. Each of these two boxes has an Ethernet connection to the Internet, and has an Ethernet connection running as HSRP.

My question is this... I understand that a preempt statement will make the router with the highest priority become the Active Router. I am not sure where to put the preempt statement,,,does it go on the Primary or the secondary.

Also, should I set up the HSRP tracking statement on both boxes to monitor the interface connected to the Internet?

Thanks!

Kevin Melton

KMNR Network Resources, Inc.

Re: HSRP Preempt and tracking questions

sundar.palaniappan — Wed, 02 May 2007 14:29:40 GMT

Kevin,

Under normal circumstances the 'preempt' command is configured on the primary hsrp router but if you are tracking another interface then 'preempt' should be configured on both devices. This would ensure the lower priority router can become the active router when the primary router's tracked interface goes down.

HTH

Sundar

Re: HSRP Preempt and tracking questions

royalblues — Wed, 02 May 2007 14:34:24 GMT

Kevin,

Ideally you should have the Preempt and the tracking command on both the routers so that the router with the highest priority becomes the active router.

when you do this, the moment a router senses a link failure it will reduce its HSRP priority and since preempt is configured on both the routers, the second router will take the active role.

If you have the preempt configured only on the primary router, a link failure on this router would not cause the HSRP state change as the router is still active. so packets still treach this router only to be sent back to the standby router for routing (provided you have proper routing in place)

HTH, rate if it does

Narayan

Re: HSRP Preempt and tracking questions

Kevin Melton — Wed, 02 May 2007 16:47:10 GMT

Based upon your answer (thank you), would the following config work for this??

S1-BRI00 config: this is the ?PRIMARY?

Int f0/1

Ip address 216.30.179.130

standby 1 ip 216.30.179.129

standby 1 preempt

standby 1 priority 100

standby track f0/0

S1-BRI01 config: this is the ?STANDBY?

Int f0/1

Ip address 216.30.179.131

standby 1 ip 216.30.179.129

standby 1 preempt

standby 1 priority 99

standby track f0/0

Re: HSRP Preempt and tracking questions

royalblues — Wed, 02 May 2007 16:52:56 GMT

The config looks ok..

I think you missed the standby group number with the track command. I think was a typo

standby 1 track f0/0

HTH

Narayan

Re: HSRP Preempt and tracking questions

sundar.palaniappan — Wed, 02 May 2007 18:53:48 GMT

Kevin,

I see one potential issue that would require the use of HSRP enhanced object tracking feature. Since you are tracking an Ethernet interface which mayn't always go down when it's not passing data which would cause HSRP tracking to not work as intended. That's when HSRP enhanced object tracking can come in handy. Take a look at the following link for more info.

http://cisco.com/en/US/products/sw/iosswrel/ps1839/products_feature_guide09186a00801541be.html#wp1027129

HTH

Sundar

Re: HSRP Preempt and tracking questions

Kevin Melton — Wed, 02 May 2007 20:04:16 GMT

You were correct in assuming I had mistyped. Obviously i need to configure the instance number to match....

thx