How many HSRP groups possible 255 or 256?

[ashok_boin]

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.

[jezerski]

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

[rgodden]

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.