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Reusing HRSP group numbers of Sup1/MSFC1

Is it safe to reuse HSRP group numbers on a Sup1A/MSFC1/PFC1? We have around 40 VLANs where, currently, the HSRP group number is the same as the VLAN number. I've noticed that in recent MSFC code, there have been issues with HRSP group numbers above 16 (CSCdx32496), with a PFC1 but these have actually been fixed in the latest code. However the PFC2 still has the limit of 16 HSRP groups, so any upgrade to PFC2/MSFC2 will require a configuration change anyway, so would it be better to do it now as we are in the process of an HSRP reconfiguration?

We have four MSFCs in two chassis (not using SRM), and all VLANs need to be defined on all four MSFCs (for HA). We couldn't do this initially, due to the migration from a "flat" network design. Even and odd VLANs are balanced across the two 6500s, but how best should the VLANs be balanced across the MSFCs (in terms of active/standby roles)? Just using the one MSFC in each chassis for even/odd VLANs, would mean that the other two MSFCs are not fully utilised. However, if the active MSFC for each VLAN is balanced across all four MSFCs then the configuration becomes more complex (i.e. it's not simply an even/odd decision, but a 4-way decision as to which MSFC is the HSRP Active router for a specific VLAN).

New Member

Re: Reusing HRSP group numbers of Sup1/MSFC1

yes you can reuse the hsrp group numbers but remember the mac-address would be the same for the virtual IP adddress in the vlans having the same hsrp group. But it should be of no concern if you have cisco network. Some non-cisco switches maintain a single mac-address table and they don't like the same mac-address on different vlans. Cisoc maintains per-vlan mac-address table and hence it is okay.

SRM is recommended. Having 4 Active MSFC will be complex for routing. SRM is the way to go.


Re: Reusing HRSP group numbers of Sup1/MSFC1

Thanks for your comments. I take it there aren't any issues with running HSRP between the chassis, and SRM within the chassis?

Cisco Employee

Re: Reusing HRSP group numbers of Sup1/MSFC1

I don't foresee any issues between HSRP between the chassis, and SRM within the chassis.

New Member

Re: Reusing HRSP group numbers of Sup1/MSFC1

That is the recommended method.

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