Flapping mac in vlan 1

[chpmotry]

Hi guys. 

I have a network with many hubs. And i have timeout sometimes in my network and im showedthis  in my 2960 switch this loggs.

My network topology is:

 

 all of the port of these switches are on vlan 1 .

What i doing to solve this problem?

[pieterh]

each switch builds a MAC address table for each connected device
plus a table for MAC addresses reachable via the uplink to another switch
the log means that the 2960 switch learns it's own locally connected mac addresses back from another network device

this can happen because some of your network devices (possibly a cam) are using the same mac addresses
-> use the command "show mac address table" on all your switches to detect IF indeed is a mac address is used multiple times
you can also use "show mac address-table address xxxx.xxxx.xxxx.xxxx " to search for a specific address
==>> this is the first to investigate

OR it can mean some communication of mac adress learning is disturbed
e.g. because the microtik links have too long delay

I also advise to replace the D-link hub (if it really is a hub)  with a switch

another advise  is segmenting your netwerk by converting your mikrotik links to routed links (L3,  instead of switched = L2)
that makes you network more robust but also a little more complex -> you need to train a bit for networking

[marce1000 · Accepted solution]

         - Make sure you have no loops in the network, 

 M.

[fniccola · Accepted solution]

ciao!

all mac-addresses into logs are related to a cam (verify them on a mac address lookup site)
could be present a loop... basically the switch is seeing the same source mac from two different ports.

let me share with you some troubleshooting steps:

1. verify the entire topology from physical point of view,
make sure for example, that on the interfcace fa0/19 there is only a cam or a group of cams.

2. verify the spanning-tree for vlan 1 on the switch (configuration and state)

3. verify the cpu level (processes and interrupts) during the problem

TKK
FabioN