Cisco Switch flashing steady green/orange

[abillybob]

Hi All

 

So we had a problem a while back where a fibre cable got broken and we got it fixed by an engineer. The fibre in question is used to trunk a 2960x stack to a 2960s stack in another building.

 

Since they fixed it I went to the 2960s stack to ensure the link was up and then went back to re-configure the two ports and get them connected again which worked and I could ping the switches on both ends.

 

Now though some strange goings on have happened, for some reason the 2960x stack is flashing steadily between green and orange on that port, the 2960s however is not. The link is still up although will drop intermittently forcing me to shutdown and open the port each time this happens!

 

Any ideas what this could be I'm hoping you won't say it's because the cable is still knackered?

[FN-GM]

When it is down can you run

 

Show Int Status

 

It will tell us what state the port is in.

[FN-GM]

Also do you have more than 1 link to the switch?

 

It could be spanning tree related or it could mean there are loads of errors (something wrong with cabling).

 

 

Can you also run

 

Show Int (name of interface)

Edited April 20, 2018 by FN-GM

[abillybob]

Well I say "down" but the port doesn't really go down per se. The uplink light is still there and looks the same it just means that intermittently random things are dropping off the network or unable to connect to terminal servers but when I shutdown and no shutdown the port it all connects up fine again for a while until it does it again.

[FN-GM]

Running this command should tell us of any issues

 

Show Int (name of interface)

 

Thanks

[abillybob]

Here you go pal

 

[FN-GM]

Perfect.

 

You see that high number next to runts. On a normal connection this would be 0. A runt is a packet that is too short or "broken". The data is getting lost or stopped being sent part way through its transition down the cable.

 

It could be 3 things.

 

1. A duplex mis-match. If these are manually configured on both sides of the link but one doesn't match the other. The same command on the switch on the other side of this link will confirm / rule this out.

2. Faulty SFP.

3. Something wrong with the cabling.

 

Given you have just had your cable repaired I think option 3 is the most likely. Do you have any spare pairs you can switch to? 1 & 2 can be ruled out quite easy.

 

Once you have done some testing and want to check what you have done has worked you can clear the counters by one of the following:

 

To clear ALL interface counters: clear count

 

To clear one specific interface counter: clear count

Edited April 20, 2018 by FN-GM

[abillybob]

Cheers for the info mate and for the video. I'll watch it tonight!

 

1. I don't think I have manually set the duplex? I have checked by doing a show run command that all commands are the same on each switch? Is there anything else I need to check?

2. The SFP module should be ok as this was working fine before the cable got broken?

3. My thoughts too, he's a bit of a funny chap has been out 4 times with various issues on this cable since he fixed it the first time. I'm not looking forward to contacting him again so I'm hoping no1 is the issue!

 

If I run that clear count command on that interface will it drop the connection for a while do you know and will it stop the lights flashing? I'm worried if it stops the light from flashing we'll have no proof then the cable is damaged?

[FN-GM]

1. You should see it on the show runn command. You can also see it on Show INT

2. Could it have been banged of damaged during the repair? I would swap it with a spare and see what happens.

 

The clear command will not drop the connection. It will just clear the stats from that output you sent. You would clear after they repair the link to test if it has worked.

[FN-GM]

How did you get on please?