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New Member

link flap problem?

Hello everyone,

Quick question about what causes a "link flap failure"

Here is the output

11-07-2005 18:48:38 Local7.Warning 172.16.208.184 1737: *Mar 13 05:47:09.196: %PM-4-ERR_DISABLE: link-flap error detected on Gi0/1, putting Gi0/1 in err-disable state

11-07-2005 18:49:10 Local7.Error 205.110.152.19 9281: 1w3d: %LINK-3-UPDOWN: Interface FastEthernet0/5, changed state to up

11-07-2005 18:50:53 Local7.Warning 172.16.208.184 1738: *Mar 13 05:49:23.765: %PM-4-ERR_RECOVER: Attempting to recover from link-flap err-disable state on Gi0/1

11-07-2005 18:50:55 Local7.Error 172.16.208.184 1739: *Mar 13 05:49:26.137: %LINK-3-UPDOWN: Interface GigabitEthernet0/1, changed state to up

I leave the errdisable recovery on and it brings the port back up once the timer goes.

What causes this link flap?

Thanx

5 REPLIES

Re: link flap problem?

Hi Friend,

Can you please update what is connected to that port. It can also be due to late collisions because of mimatch of duplex and speed settings between switch and machine connected.

Regards,

Ankur

New Member

Re: link flap problem?

Hello there 8)

From the previously mentioned switch:

Gi0/1 TRUNK TO ISF159 connected trunk a-full a-1000 1000BaseLX

CONTRA#sh run | begin Gig

interface GigabitEthernet0/1

description TRUNK TO AS

switchport mode trunk

!

This is from the connected switch:

Gi0/1 TRUNK TO CONTRACTO connected trunk a-full a-1000 1000BaseLX

AS#sh run | begin Gig

interface GigabitEthernet0/1

description TRUNK TO CONTRACTORS

switchport trunk encapsulation dot1q

switchport mode trunk

no ip address

!

Thanx for any help

New Member

Re: link flap problem?

Grr, happened again. Same switch, exact same log entries, just different times.

Anyone have any idea what causes this "link flap" problem?

Re: link flap problem?

HI Armeqeden,

Its mostly not a config problem because if it was it should haven been flapping continuously.

Now because it is flapping after sometime mostly I think it is a physical layer problem.

As you confirmed that the duplex and speed setings are auto you can give a try with duplex full and speed 100 and also try changing the physical cable.

Regards,

Ankur

Re: link flap problem?

I would agree that it is something physical. I had a very simular issue and solved it by changing from Auto/Auto on a GI interface and set the speed to 1000 on both sides (no need to set the duplex because it defaults to full for 1000Mb connections),just set the speed. I think it might be a problem with the Autonegotiate part. Also, how long is the physical cable that connects these two switches? If the cable is faulty or too long it will also cause these link-flaps.

Hope this helps,

Mike

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