Cisco Support Community
Showing results for 
Search instead for 
Did you mean: 
You may experience some slow load times, errors, and slight inconsistencies. We ask for your patience as we finalize the launch. Thank you.

Welcome to Cisco Support Community. We would love to have your feedback.

For an introduction to the new site, click here. If you'd prefer to explore, try our test area to get started. And see here for current known issues.

New Member

moving MACs

I have a 2924_XL s3witch that continuosly gets the following message:

Nov 28 08:16:55 EST: %RTD-1-ADDR_FLAP: FastEthernet0/1 relearning 11 addrs per min. debug info shows macs on different ports every minute.

Can anyone explain this to me. everything seems to be working fine...

  • Other Network Infrastructure Subjects

Re: moving MACs


RTD-1-ADDR_FLAP [chars] relearning [dec] addrs per min

Explanation Normally, MAC addresses are learned once on a port. Occasionally, when a switched network reconfigures, due to either manual or STP reconfiguration, addresses learned on one port are relearned on a different port. However, if there is a port anywhere in the switched domain that is looped back to itself, addresses will jump back and forth between the real port and the port that is in the path to the looped back port. In this message, [chars] is the interface, and [dec] is the number of addresses being learnt.

Action Determine the real path (port) to the MAC address. Use debug ethernet-controller addr to see the alternate path-port on which the address is being learned. Go to the switch attached to that port. Note that show cdp neighbors is useful in determining the next switch. Repeat this procedure until the port is found that is receiving what it is transmitting, and remove that port from the network.


-amit singh