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New Member

Multigroup HSRP Question: Same Group on multiple interfaces

I have a question regarding multigroup HSRP.

We have (2) Catalyst 6506 L3 switches (core1 and core2). On each switch we have (2) VLAN interfaces - VLAN1 and VLAN2. On each interface, we're running multigroup HSRP with 2 standby groups.

The question involves the HSRP group numbers (see below) and if this setup will work and/or cause problems.

core1:

Interface VLAN1

standby 1 group - ACTIVE

standby 2 group - STANDBY

Interface VLAN2

standby 1 group - STANDBY

standby 2 group - ACTIVE

core2:

Interface VLAN1

standby 1 group - STANDBY

standby 2 group - ACTIVE

Interface VLAN2

standby 1 group - ACTIVE

standby 2 group - STANDBY

The question:

Can we use the same HSRP group numbers on VLAN1 and VLAN2, or do they need to be different?

My theory:

The HSRP virtual MAC address is determined by the standby group number. Each VLAN has it's on MAC address table. Therefore, it should be valid for one VLAN to see the HSRP virtual MAC address as being local (sent to router) and for the other VLAN to see the virtual MAC address as being remote (send through switch port).

Can someone please confirm?

Thanks,

Jordan Bean

Webcore Technologies, Inc.

bean@webcoretech.com.

2 REPLIES

Re: Multigroup HSRP Question: Same Group on multiple interfaces

New Member

Re: Multigroup HSRP Question: Same Group on multiple interfaces

Thanks! This was exactly what I was looking for. I only found the FAQ and not the document with the answer. For anyone interested in this:

Q. What is the implication of using the same HSRP group ID on multiple interfaces?

A. When you define the same HSRP group ID on multiple interfaces, they share the same HSRP Virtual MAC address. In most modern LAN switches, there would be no issues because they maintain a per-vlan MAC address table. However, if your network contains any third party switches, which maintain a system wide MAC-address table regardless of VLAN, you may experience problems.

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