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New Member

HSRP problems

We are running HSRP between a RSM and a 4700 router. The RSM is routing all our VLANs, and the 4700 handles all our ISDN lines.

We are running MRTG to monitor these routers, and we found that the CPU utilization on the 4700 tend to mirror that of the RSM, ie. If the RSM's CPU goes up to 15%, the 4700's will go up to 15% as well.

To me, this sounds wrong. If the RSM routes all the VLANs, then surely the 4700 will just cruise almost all day long?

We had the case recently where the RSM's CPU went up to 100%, but we couldn't find the process that was killing the CPU!! Needless to say, the 4700 followed soon. After the RSM was rebooted, it stayed at below 10% CPU, and the 4700 gradually went down as well.

Any thoughts on what it could be that can kill a RSM like that (and, of course, the HSRP issue)?

  • Other Network Infrastructure Subjects
New Member

Re: HSRP problems

You could have a problem with snmp, for me. If you use MRTG, you could stuck a router with a SNMPGet. For exemple, a SNMPGet on routing table could produce some kind of trouble.

Perhaps, you have a HPOV with an automatic discover activated.

You can look for a bug in the bug toolkit with keywords snmp, cpu, and you see some very interesting bugs.


Re: HSRP problems

Do you have the HSRP active side set to the RSM ? If the standby router is actually the rsm and not the isdn router than all your traffic would be routed out the isdn side and then back over to the RSM side . Are you tracking a serial interface to make it fallover and then have a default route pointing towards the isdn side ?

New Member

Re: HSRP problems

Thanks for the replies! HSRP is active on the RSM, and on standby on the 4700. Both routers are actually our LAN routers (except for the 4700 which does ISDN as well), and both have exactly the same VLANs configured on them.

I have double checked to make sure that all VLANs are active on the RSM, and standby on the 4700.

I am actually using MRTG to monitor the CPU utilization of these routers - no other interfaces are monitored...

New Member

Re: HSRP problems

You may also want to check you broadcast traffic rate on the subnets/interfaces that are common to both boxes. It may be a broadcast storm that is causing the CPU's to increase at the same time.

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