Re: Mac flapping between two port of a port-channel.

beohu · ‎06-04-2020

Hi guys,

My port-channel (gi0/47, gi0/48) of 2960 switch connected to a stacked 3750 (contain 02 switches stacked, on 1/0/24 and 2/0/24).

Sometimes the 2960 switch is suspended (I have to restart it to make it works), on the 3750 I see the log like this at the time the 2960 switch suspended:

*May 4 23:24:53.829: %SW_MATM-4-MACFLAP_NOTIF: Host e454.e879.0144 in vlan 1 is flapping between port Gi2/0/24 and port
Gi1/0/24
*May 4 23:24:54.031: %SW_MATM-4-MACFLAP_NOTIF: Host e454.e878.ffb4 in vlan 1 is flapping between port Gi1/0/24 and port
Gi2/0/24
*May 4 23:24:54.257: %SW_MATM-4-MACFLAP_NOTIF: Host e454.e879.26a3 in vlan 1 is flapping between port Gi1/0/24 and port
Gi2/0/24
*May 4 23:24:54.643: %SW_MATM-4-MACFLAP_NOTIF: Host 1866.da3b.3a14 in vlan 1 is flapping between port Gi2/0/24 and port
Gi1/0/24
*May 4 23:24:55.499: %SW_MATM-4-MACFLAP_NOTIF: Host e454.e878.fb12 in vlan 1 is flapping between port Gi1/0/24 and port
Gi2/0/24
*May 4 23:24:56.505: %SW_MATM-4-MACFLAP_NOTIF: Host 6400.6a0b.ff65 in vlan 1 is flapping between port Gi1/0/24 and port
Gi2/0/24
*May 4 23:24:57.604: %SW_MATM-4-MACFLAP_NOTIF: Host f8bc.129a.db7a in vlan 1 is flapping between port Gi2/0/24 and port
Gi1/0/24
*May 4 23:25:02.856: %SW_MATM-4-MACFLAP_NOTIF: Host f8bc.1299.d9eb in vlan 1 is flapping between port Gi1/0/24 and port
Gi2/0/24
*May 4 23:25:03.703: %SW_MATM-4-MACFLAP_NOTIF: Host f8bc.129b.3a63 in vlan 1 is flapping between port Gi2/0/24 and port
Gi1/0/24

Do you know any reasons can make the port-channel is the cause of loop (as shown on the log)? Please help.

kalyanjewellers92035 · ‎06-04-2020

cards from 4506-E and plug it in the 4507R-E worked for me!

Pls try this . Please try other steps as mentioned/

May port problem can be there!

Thanks

pieterh · ‎06-04-2020

do you also have logging from the 2960 switch?

the mac-flap together with the suspended state may indicate the port-channel is not configured correctly

check both ends of the configuration !!!

check if member-port has no mismatch with port-channel config

beohu · ‎06-04-2020

When the 2960 SW suspended, I couldn't log in by telnet or console to get the log, I must restart it to recover network that the switch cover.

After restart the 2960 SW, I checked port-channel on both ends, it seems configured properly.

romanroma · ‎06-04-2020

Can you share port-channel/ether-channel configuration. This appears to be an issue in the channel configuration, since a layer 2 loop is taking place.