C2960L-8TS-LL

[parvez.akhtar11]

Hello all,

We are a campus environment. We just introduced small port switches(8 ports & 16 ports---c2960 model). Since when we inducted these switches, we are getting MACFLAP errors on trunk link. We have same config. on uplink. This error is only on these small port switch.

Following is type of error:

Apr 26 2017 16:48:06 PK: %SW_MATM-4-MACFLAP_NOTIF: Host b8ca.3a87.9788 in vlan 25 is flapping between port Gi1/0/39 and port Gi1/0/41
Apr 26 2017 16:48:06 PK: %SW_MATM-4-MACFLAP_NOTIF: Host b8ca.3a87.9788 in vlan 25 is flapping between port Gi1/0/41 and port Gi1/0/39
Apr 26 2017 16:55:57 PK: %SW_MATM-4-MACFLAP_NOTIF: Host d4be.d9c2.c528 in vlan 60 is flapping between port Gi1/0/41 and port Gi1/0/49
Apr 26 2017 17:03:10 PK: %SW_MATM-4-MACFLAP_NOTIF: Host 000f.fe7e.c888 in vlan 60 is flapping between port Gi1/0/49 and port Gi1/0/41

Any support/suggestion is appreciated...Thanks 

[eduardopozo56]

It seems like you have 2 ports cabled between two switches, and a port-channel missconfigured. Seems like g1/0/39 and g1/0/41 (uplinks) are members of an etherchannel on the remote switch, but not on the one where you see the error logs.

[parvez.akhtar11]

thanks for your reply.

g1/0/39 is providing uplink(trunk port) to small port sw. and g1/0/41 is providing another trunk to another small switch.  g1/0/49 is uplink of this SW to distribution SW which has port channel config with core sw. Port channel config is identical on both ends

We have checked all physical cabling. It seems right

[eduardopozo56]

The example log shows that the same host (b8ca.3a87.9788) is flapping between ports 39 and 41. So either:

- There is a L2 loop on your network, the two "small switches" connected to ports 39 and 41 are also connected together (or bridged by a host) and this loop is not being caught by STP due to bug or missconfig

- The host is dual-homed to these two switches.

As you also have mac-flapping between one of the "small switches" and your distribution switch, i would bet for a L2 loop.

[parvez.akhtar11]

But there is no increase in CPU level of either switch if there is L2 loop( less that 25%).

We have switch to which only one small port (8-port C2960) is connected. and that is also behaving same.

Apr 26 18:51:38: %SW_MATM-4-MACFLAP_NOTIF: Host b8ca.3a8d.ac12 in vlan 25 is flapping between port Gi0/2 and port Gi0/1

gi0/2 is uplink for small sw. gi0/2 is uplink to dist. SW which has port channel with main core SW.

[Reza Sharifi]

Hi,

Can you post the config for all these ports?

HTH

[parvez.akhtar11]

interface GigabitEthernet1/0/39
description *** GF-GYM-SW-2960-16TS-SW.153 ***
switchport trunk native vlan 99
switchport mode trunk
switchport nonegotiate

and

description *** Basement pdm room SW.166 ***
switchport trunk native vlan 99
switchport mode trunk
switchport nonegotiate