09-20-2018 08:05 AM - edited 03-08-2019 04:12 PM
Hi everybody
I have got a problem with a Stack of 4 WS-C3750X-24T-S IOS 15.0(2)SE9
In the cache, I see a mac address associated with a portchannel (Po7) to another switch.
eec2.019b.d16f DYNAMIC Po7
But I see in a switch connected to this stack by another portchannel (Po1) this mac address arriving as a destination : In theory it is not possible ! (It is an exemple because it's happening with other mac addresse, other switches and other portchannel).
If somebody has an idea ...
Sincerly
Laurent
09-20-2018 12:01 PM
Hello Laurent,
How did you spot this? With a monitor session on the other switch?
This looks indeed strange, it could happen when the mac-address table is full because the switch will flood all the packets..
Could it be that you have the same mac address but on different vlans? Try to use the command "mac-address-table notification mac-move" so you can spot if eventually the mac is flapping around. A good look a the logs could shed some light as well.
What kind of device has a mac-address starting with "eec2"?
Cheers,
ADP
09-21-2018 02:59 AM
Hi
I spotted this issue with a tcpdump on a server that should never see this address.
the mac-address table is not full and the mac is not flapping.
the mac address is a virtual mac address of a VM by Xen Server and in an only one vlan.
I really don't understand how it is possible !
Regards
Laurent
09-21-2018 05:15 AM
Do you see this traffic constantly or do you just see a bunch of packets randomly?
Does the server who owns that IP get traffic at all?
Have you tried to clear the mac address table?
09-21-2018 06:23 AM
no it is not permanent so it is difficlt to be sure if the paquets arrive to the right server.
I have just tried to clear the mac table and I am monitoring
09-24-2018 01:47 AM
After the clear mac address-table I was confident about fixing the issue ... but after a few minutes the problem came back !
I will open a case to the support (maybe a bug in the IOS).
Thank you for your help.
Laurent
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