[c-nsp] Too much HSRP traffic - how to limit?

[Phil Mayers]

Neal R wrote:
> 
>    I have some cat 3750 with 125ms hello/375ms hold time in a network
> with a lot of voice traffic. We like the fast failover we get with these
> times but we've got one sort of host that really whines about 32
> multicast packets/second. I've tried all sorts of methods to limit
> traffic destined for 224.0.0.2 on a couple of member ports of a
> particular vlan but I'm not coming up with an answer. Output policing?
> Not supported. The storm-control command limits *input* on ports. Access
> lists seem to be limited to the vlan interface themselves rather than
> the physical port.
> 
>    I can't be the only one facing this problem - anyone got a recipe for
> this particular issue?

It's particularly annoying isn't it? I really don't understand what the 
HSRP designers were thinking. Quite why it doesn't have periodic (slow) 
discovery packets and unicast (fast) hellos I don't know. Better yet, an 
adjacency process.

The latter in fact would facilitate removing the connected route from 
the standby (if the adjacency were out-of-band e.g. loopback-loopback) 
and coalescing of multiple groups.

Back in the real world however...

Do the downstream switches have output ACLs? Because the HSRP group is 
in the local-subnet multicast range it can't be IGMP-snooped and output 
ACLs are about the only way you can deal with it that I've found.