HSRP - Between a 2600 and a 1700

Unanswered Question
Nov 29th, 2007

Dear All,

ist it possible to get hsrp working between a 2600 IOS 12.3 and a 1700 IOS 12.1?

I am trying to build some redundnacy into a very badly designed network.

Any suggestion received with thanks.


I have this problem too.
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Richard Burts Thu, 11/29/2007 - 09:38


If it is a live site then you need to proceed with caution. But certainly the 2 platforms are compatible to run HSRP and the 2 versions of code should be compatible. So there should not be any real issue in setting up HSRP there.

In my experience of setting up HSRP on existing networks/subnets, there is an advantage if you take the existing router interface address (which is the configured default gateway on the end stations in the subnet) and use that for the virtual/shared address and configure a new address on the router interface it makes the transition to HSRP easier since you do not need to change configuration on the end stations.



milan.kulik Fri, 11/30/2007 - 05:19


what Rick suggested is correct with one warning:

You are changing the MAC address related to the default gateway this way.

Which might bring you a trouble with an ARP cache aging on some (UNIX mostly) machines.

But the default ARP cache timer is 4 hours, so not a big trouble in fact.

If doing those changes remotely, there's also a good practice to use "reload in 15" command before starting config changes.

This would bring your connection back if anything goes wrong and you lose your connection (I remember an IOS bug on Cisco1721 making the router "frozen" after HSRP activated).



Richard Burts Sun, 12/02/2007 - 15:12


Both of the points that Milan makes are valid and are something to think about.

In my opinion when you compare the impact of possibly confusing the ARP table on some end stations for a couple of hours (maybe) vs the impact of leaving the original address on the router interface, configuring HSRP with another address, and having to manually reconfigure the default gateway of all devices on that subnet, I know which one I prefer. Of course it is your network and you should choose the one that seems least impact to you. (it has been a long time since I looked and I do not remember whether IOS does a gratious ARP when it starts HSRP, but if it does then the issue of end station ARP table is taken care of)

The advice about scheduling a reload before starting remote maintenance is a good suggestion. If something goes wrong with your config changes it will restore the router to the config before changes were made. And if your changes are successful then you just cancel the reload.




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