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HSRP platform limitation

I have a 6509 running 12.1(6)E1 and I successfully created 18 distinct HSRP groups. I have a 6513 running 12.1(8b)E7 and when I attempted to make the 17th HSRP group, I got a message saying it couldn't due to a "Platform Limitation".

How many HSRP groups are permitted on a 6509 and 6513? I was sure it was either 255 or 1024 but can't the document to back that up.

I find it hard to believe that the 6509 can handle the quantity but the 6513 can't.



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Re: HSRP platform limitation

I did find my reference at 255 HSRP group numbers are suppose to be supported (Building Cisco Multilayer Switched Networks - by Cisco Press)

Here is the exact message I get from the 6513:

"More than 16 standby groups not supported in this platform."

Community Member

Re: HSRP platform limitation

16 unique standby group limitation is the limitation on the sup2/pfc2/msfc2.

The previous didn't probably have software check to prevent or warn users from configuring more than 16 distinct groups.

Now this 16 unique group limitation is not a big problem in usual network. You can use the same group # on many vlans and still use different hsrp virtual address. for example if you have 32 vlans, you can use 1-16 for the first 16 vlans and then again 1-16 for the next 16. HSRP addresses will obviously be different. The only caveat is that hsrp mac address for each group is fixed. so you would same virtual mac for vlan 1 and 17 in the above example. But our switches maintain cam-table per vlan so it should be okay.

Community Member

Re: HSRP platform limitation

You've run into a limitation of the Cat 6500 PFC2, which your 6513 likely has. Per Cisco, the PFC2 only supports a maximum of 16 unique HSRP group numbers. Prior to this the MSFC1/PFC1 could support 255 unique HSRP groups like Cisco IOS routers.

Prior to the newer releases of Cat6500 IOS, there were bugs associated with HSRP that required use of unique group number per VLAN interface. This was done to remove the possibility of problems due to using the same virtual MAC address (and associated issues with election of the active router; see links below).

Somehow, Cisco has corrected this for PFC2, at least I hope so. We have newer Sup cards with MSFC2/PFC2 and new code and have not run into any problems thus far. You should be safe to configure your interfaces using the same HSRP group number (default 0 or another number).

Caveat is if you need to configure bridging on MSFC. See link

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Re: HSRP platform limitation

Thanks for the info.

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