HSRP group multiple vlans different priorities

[p.devalck]

Are problems possible when using different vlans in a same HSRP group when setting the HSRP priorities differently for different vlans in the same group ?

Are the HSRP priorities for a same group treated separately for different vlans ?

The number of VLANs is such that for some older L3-switches the number of vlans (to be covered by HSRP) vastly exceeds the number of possible HSRP groups.

In the example below the active HSRP master would be different for the different vlans in the same HSRP group.

Is that a problem (especially with L3 switches of Catalyst 3550 and/or 3560 series ?

Typical config looks like :

Switch 1 :

 vlan A

  ip address X.X.X.2

  standby 1 ip X.X.X.1

  standby 1 prio 90

  standby 1 preempt delay min 30

vlan B

 ip address Y.Y.Y.2

 standby 1 ip Y.Y.Y.1

 standby 1 prio 110

 standby 1 preempt delay min 15

Switch 2 :

 vlan A

  ip address X.X.X.3

  standby 1 ip X.X.X.1

  standby 1 prio 110

  standby 1 preempt delay min 30

vlan B

 ip address Y.Y.Y.3

 standby 1 ip Y.Y.Y.1

 standby 1 prio 90

 standby 1 preempt delay min 15

[chrihussey · Accepted solution]

That shouldn't be a problem at all.

Many times I do just that to achieve a form of load balancing with dual homed access switches to two distributions. This way the default gateway for the VLANs is distributed between the two distros.

I also prefer to keep the number of HSRP groups to a minimum, one or two depending on size.

Hope this helps

[p.devalck]

With HSRP there are some restrictions regarding the number of VLANs one can include in HSRP.

In the 3550 switches the number of HSRP groups is limited (to 16) and in each group only vlans of a same 16-block are allowed, so e.g. vlans 128 to 143 in an HSRP group take up 1 (of the 16) HSRP group.
Whereas block 127 - 142 takes up an HSRP group count of 2 (1 group for vlan 127, the second for the others).
A maximum of 256 vlans can therefore be covered by HSRP.

In the 3560 I ran into a limitation of 32 vlans for HSRP, as the implementation has clearly changed.
It seems that in some 3560-E series (for service providers ?) this limitation has been eased and far more vlans can be covered.
So there the individual switch model is the deciding factor.