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Problems with the MAC Addresses in a 4006 switch?

I'm having an interesting problem at one of my sites. We'll call it site A.

At site A we have 3 4006 switches fully loaded or close to fully loaded each. They span 3 floors. One of the switches is the "core" switch if you will. The other two switches connect to it and it links back to my main facility over a gigaman circuit. Back at the main facility, the Gigaman circuit terminates on another 4006 switch that also terminates a lot of other similar but smaller sites like site A.

Here's the problem I'm having.

From time to time, somebody at site A will report that they can no

longer connect to the network. The fix is, to go out there and administratively set the MAC address to something else. Then it works for a day or 2 and breaks again. So, we change the MAC again. It's like the old MAC just stops working. Where do you start with something like that. It HAS to be a switching issue doesn't it?

Should I increase or decrease MAC aging? What do you guys think on that one?

Reply to
Cpt_CAM
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Post the software version in use on the switches having the issue.

Reply to
Merv

You could consider trying the clear mac-a xxxx.xxxx.xxxx IOS clear cam dyn xx:xx:xx:xx:xx ?? CAT IIRC

I would possibly avoid clearing the whole table if you suspect MAC address issues in the network

OR

if you have a lot of devices and have old supervisors in the 4006.

Do this on all switches.

At least this may mean that you don't need to leave your seat:)

In the first supervisor on the 4006 address learning was entirely in software and it's best address learning rate was very low. The current ones probably do not have this limitation.

Use the sh cam dyn or whatever to troubleshoot by finding out what ports the switches think the problematic mac is on and compare that with your knowledge of the expected path.

Newer IOS kit has traceroute mac which may take some the the work out of it but with only 3 switches that should not be too bad.

Duplicate MAC addresses are not entirely unknown although I have never seen one.

Reply to
anybody43

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