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How many HSRP groups possible 255 or 256?

Dear all,

Maximum of how many HSRP groups can we configure? 256 or 255.

Because whenever configuring, the range it gives as "0-255", but in books it has given max of 255 only.

Thanks in advance...

Regards...

Ashok.

With best regards... Ashok ----------- Pls kindly rate if helpful or answered your question.
2 REPLIES
New Member

Re: How many HSRP groups possible 255 or 256?

Never trust what technical books say at face value. Instead, use your own thinking and experiments. If you take a look at the RFC for HSRP (yes, even though HSRP is Cisco Proprietary, they wrote an RFC #2281) you can see that the group field in the packet format is 8 bits. That gives you a theoretical 256 different possibilities. To confrm this in a practical sense, set up a router and build HRSP group 0 and another HSRP group 255. I tested this and had no issues. Therefore, your answer is 256.

r3#sho stand brie

P indicates configured to preempt.

|

Interface Grp Prio P State Active addr Standby addr Group addr

Ethernet0/0 0 100 Active local unknown 1.1.1.1

Ethernet0/0 255 100 Active local unknown 10.1.1.1

HTH

-Joe

New Member

Re: How many HSRP groups possible 255 or 256?

Q. What are the limiting factors that determine how many standby groups can be assigned to a router?

Ethernet: 256 per router. FDDI: 256 per router. Token Ring: 3 per router (uses reserved functional address).

Note: 4x00 series and earlier do not have the hardware required to support more than one MAC address at a time on Ethernet interfaces. However, the Cisco 2600 and Cisco 3600 do support multiple MAC addresses on all Ethernet and fast Ethernet interfaces.

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