2

I know the overview of HSRP and that election depends on priority. I also know that only active and standby routers send hello messages every 3 seconds. But when the routers are first configured with HSRP, how do they exchange message and elect the router with highest priority?

5

Cisco has many documents to explain such things. For example, Hot Standby Router Protocol (HSRP): Frequently Asked Questions:

Q. If there is no priority configured for a standby group, what determines which router is active?

A. The priority field is used to elect the active router and the standby router for the specific group. In the case of an equal priority, the router with the highest IP address for the respective group is elected as active. Furthermore, if there are more than two routers in the group, the second highest IP address determines the standby router and the other router/routers are in the listen state.

Note: If no priority is configured, it uses the default of 100.

  • Thank you so much! But I'm looking at even deeper level. I'm trying to understand exactly how the packets are shared when the routers are first configured with HSRP. Theoretically we know that priority is the metric to elect the active router. But how do other routers participate in this election? Do they all exchange hello packets? Because all the articles say that only active and standby routers send hello packets. – iiTechii Apr 2 at 22:20
  • It's not an "election" in the classic sense of the word. The routers come up listening for frames in the group for which they are configured, and each assumes it is the active router, until it receives a superior frame for the HSRP group to which it is listening. As I explained, Cisco has many documents about this if you search for Cisco HSRP. For example Hot Standby Router Protocol Features and Functionality. – Ron Maupin Apr 2 at 22:26
  • wow! that answers my question. Thank you so much!!! – iiTechii Apr 7 at 21:37

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.