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New Member

Asymmetric Routing and HSRP

I am working with TAC on this issue, but I thought I might get some input from the community at large.

I have two CAT6509's running Native IOS. I have setup HSRP on these switches in the standard way. I am having Unicast traffic flooding on random ports across my network. After about 1 week of sending command output files and sniffer traces, TAC said I had Asymmetric Routing issues relating to HSRP and said the recommended solution is to adjust the MAC aging time on the switch to 14,400 seconds (4hrs).

I have a pretty vanilla config when it comes to networks, is this something that is common? Has anyone else had this issue?

Here is the artical detailing more about the issue.

Thanks for any advice/input.

Nitan Parikh

William Blair & Company

Hall of Fame Super Silver

Re: Asymmetric Routing and HSRP

The mismatch between the MAC aging timer (shorter) and the ARP timer (longer) is a fairly well known issue. Lengthening the MAC aging timer or shortening the ARP timer are common solutions.



New Member

Re: Asymmetric Routing and HSRP

I can also confirm this is exactly what Cisco recommended for me when I had the same issue with unknown unicast flooding.


New Member

Re: Asymmetric Routing and HSRP

Hello Nitan,

we have the same problem as you described in your message.

We adjusted the timer and the problem still exists.

Best regards

Wolfgang Mehler

Networking & Infrastructure

IT Schaeffler Group

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