Fiber trunk on errdisable state and Symbol Errors

[rocketlauncher]

Hello All,

I'm not a fiber expert and I'm hpoing someone can point me in the right direction.

I have 1000LX fiber trunk between 2 3550 switches. This trunk link goes into err-disable state quite oftenly. The reason I get on the syslog is %PM-4-ERR_DISABLE: link-flap error detected on Gi0/1, putting Gi0/1 in err-disable. I do see the flapping goign on. And I've went over Cisco docs on regards to this matter an it states that it's usually a physical problem. But my quesiotn is:

What is the best way to get to the source of the problem? Which side is the one that is bad? Is it one of interface a the switch or the fiber? How to I test them?

I've already done the following:

1) Checked trunk config. They're the same.
2) Replaced Fiber patch panels cables on both ends.
3) Looped back both fiber ports in each switch and they come up ok.
4) Tested fiber link apperently is ok. But I'm not to sure, since this was done by a subcontractor.

I want to do is pretty much, prove to managament that the switchs are ok and that the problem lies somewhere else. Thsi way we need to get our sub involved in order for them to replace the fiber run.

Also, noticed while doing a show controllers, that there where 377451 Symbol error frames on one side of the link.

What are these?

Thanks in advance for all your help.

Best Regards,

Rocket

 

[vipergg]

Usually you will get errors on one side or the other . If the errors are on the RX side that will tell you which fiber strand probably has the problem .


Symbol error frames


Gigabit Ethernet (1000 Base-X) uses 8B/10B Encoding to translate 8bit data from the MAC sublayer(layer 2) to a 10bit Symbol to send over the wire. When a port receives a Symbol, it extracts the 8 bit data from the Symbol (10 bits).


A Symbol error means the interface detects an undefined (invalid) Symbol received. Small amounts of symbol errors can be ignored. Large amounts of symbol errors can indicate a bad device, cable, or hardware.

 

[rocketlauncher]

Thanks for your reply Viper.

I'll let you know how ti goes.

 

[BuckWeet]

Try replacing the gbics if you can..

 

[burtsbees]

It may be as simple as cleaning the ends of the fiber cable jacks with alcohol...

Burt

 

[rocketlauncher]

Thanks for all your tips guys. I really appreciated.

We've already replaced the GBICS on both ends and it has happened again. The interface went into err-disable state. But this time around when performing the shut no shut sequenece the interface would not come up, it would show in a not connected state. so I went to the remote location and tested the interface myself. I did al oopback test and it came ok. so I then proceeded to replace the fiber patch cable, the interface came right up and everythig as back to normal.

These units are under contract and we have to go thorugh our contractor in order to fix any issues, but I was so frustated that they couln't figure out the problem (four months), that I had to step over some toes in order to troubleshoot the problem. I just hope this was the reason for the err-disable state on this interface.

Thanks again,

Rocket.

 

[Flyers01]

Symbol errors are most times a bad Gbic but not always

DO you get any packet loss when pinging from switch to switch

Make sure the Gbics your are using are Cisco

I would also test the fiber run from patch cable to patch cable.

Make sure your DB readings are under 2

 

[Flyers01]

nevermind my reply I didn't see you fixed the issue.