Regarding MAC table of cisco switch

[Arijit Das]

Hi All,

Myself Arijit.

I just have one small quary.

While monitoring the health of my company's network I found that the no of entries in MAC table changing rapidly and it is keep changing every time I hit the same command i.e # sh mac address-table.

Now please tell me if it is pretty normal or it is a symptom of any network issue.

Thanks,

Arijit

[kcnajaf]

Hi Arijit,

On what device are you trying this command? Is this on the production environment where you have huge volume of clients using network servces?It is quite normal that switch ports will have various entries on the MAC table, but they shouldn't be changing continously until if you have some access point connected to switch and various devices are getting connected to the AP.

Regards

Najaf

Please rate when applicable or helpful !!!

[Arijit Das]

Hello dear,

On every cisco switch in the network (4507, 3560 & 2960) and the number is keep getting changed.

There are no access point.

so please tell me how to rectify the issue.

Thanks,

Arijit

[mahmoodmkl]

Hi

have u verified your L2 toplogy for any loops.

Do feel slowness in u r network.

Thanks

[Arijit Das]

Hi dear,

Yes network sometime runs slow.

Please let me know how to detect loop or any l2 topology error.

Thanks,

Arijit

[Richard Burts]

Arijit

I would suggest that some amount of change in the MAC address table is normal. Unlike the ARP table which has a pretty long timeout the MAC address table will age out entries in a few minutes (by default). So some host on the network sends a frame and the switches add its MAC address to the table. A few minutes go by and the host is not sending any traffic and the switches remove its MAC from the table. Then the host sends another frame and the switches add it to the MAC table again.

We do not have enough information to be able to determine if the changes that you describe are in the normal range or whether they are more than normal. Can you tell us how many devices in the network, how many entries in the MAC address table, and some indication of how many change if you do the commands once per minute for a 10 minute interval?

HTH

Rick