HSRP limits on ISR4331

[tonycarr69]

I have two ISR4331 with 25 LAN facing sub-interfaces on Gi0/0/2.  They all have HSRP running.  Most have HSRP authentication.  I tried to add HSRP authentication to those that did not have it and I received the following error.

%Warning : Interface MAC address filter only supports 15 additional addresses

%And 25 HSRP groups are already configured.  The HSRP MAC address may not be added to the MAC address filter if the group %becomes active

I can confirm the "show standby capabilities" shows 15 in the potential max column. 

So I wonder has this error been displayed every time an engineer added more than 15 HSRP interfaces.  There are 9 HSRP groups shared between these 25 interfaces.

Is there any way to increase this limit.  I'm running IPBASE version 15.5.3.s3

[Giuseppe Larosa]

Hello @tonycarr69 ,

many years ago I had the same issue on Cisco 7500.

The limit is in the gigabit interface hardware the MAC address filter is the list of MAC addresses either unicast, multicast or broadcast for which the frames are carried to upper layer for further examination.

In the case of Cisco 7500 the limit was 31 MAC addresses.

However, there is a way to mitigate this limit : only the standby Active router really needs to install the VIP MAC address in the MAC address filter. So a workaround is to have a subset of subinterfaces / groups where the active router is router1 and the other where the active is router2.

However, this can become an issue if one of the two nodes fail.

Hope to help

Giuseppe

[paul driver]

Hello

What version of hsrp are you using?

[tonycarr69]

HSRP version 1. Do you think version 2 will solve this ?

[paul driver]

Hello

HSRPv2  does have a greater range of group numbers thus its capabilities are  higher 

You could try it but note v2 interfaces iare not backward compatible with v1 so those interfaces need to be running the same HSRP version

[marce1000]

 - Some additional info is also available in this thread :

           https://community.cisco.com/t5/routing/hsrp-group-limitation/td-p/3726472

 M.

[Georg Pauwen]

Hello,

on a side note, there used to be an interface command 'standby use-bia', what if you use that on your subinterfaces ?