%RTD-1-ADDR_FLAP and %LINK-4-ERROR

[christina_neo]

Hi,

Would appreciate if anyone could advise on the following errors on the switch log(details on the attached log.txt:

%RTD-1-ADDR_FLAP: FastEthernet2/1 relearning 5 addrs per min

...

%RTD-1-ADDR_FLAP: FastEthernet0/1 relearning 28 addrs per min

%LINK-4-ERROR: FastEthernet0/9 is experiencing errors

...

1) what is the cause of both FastEthernet2/1 and FastEthernet0/1, which are trunk ports relearning <##> addrs per min?

2) FastEthernet0/9 is connected to a pc. Would it be possible that the NIC on the pc that causes the %RTD-1-ADDR_FLAP log message?

Thanks.

[spremkumar]

Hi

Hope this helps..

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

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.

Recommended Action: Determine the real path (port) to the MAC address. Use the debug ethernet-controller addr privileged EXEC command to see the alternate path-port on which the address is being learned. Go to the switch attached to that port. Note that the show cdp neighbors command 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.

few cases which is very much inline with urs..

http://forums.cisco.com/eforum/servlet/NetProf?page=netprof&forum=Expert%20Archive&topic=Network%20Infrastructure&CommCmd=MB%3Fcmd%3Dpass_through%26location%3Doutline%40%5E1%40%40.ee97145/25#selected_message

http://forums.cisco.com/eforum/servlet/NetProf?page=netprof&forum=Network%20Infrastructure&topic=LAN%2C%20Switching%20and%20Routing&CommCmd=MB%3Fcmd%3Ddisplay_location%26location%3D.1dda6dde

regds

[mahmoodmkl]

Hi

There is a loop in u r network thats why the address of the PC is learned on two ports.If u have any redunadant links in ur network try disconnecting and verify it.

Thanks

mahmood

[christina_neo]

Hi,

Thanks to both for your replies.

I have a redundant link and have disconnected it from the network and it seems ok now.

However, I am wondering if the loop is caused by the following:

1) an end user who connects a hub/switch on the network with portfast enabled which causes disruption to the network? Coincidentally, when I disconnect my redundant link, the end user already removes the hub/switch from the network.

2) The faulty NIC from a pc which is the cause of it? based on the log.txt(%LINK-4-ERROR: FastEthernet0/9 is experiencing errors)

Can anyone advise if the configuration of bpdu guard helps to eliminate looping issues?

Thanks.

Christina