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Fiber link fails to pass traffic

felixnkansah
Level 1
Level 1

‎09-29-2007 10:39 AM - edited ‎03-05-2019 06:46 PM

Hello,

I am a Systems Engineer working with a Cisco Channel Partner.

A client of ours has a fiber backbone between two buildings on their campus.

The fiber terminates on a Catalyst 6509 (at the data centre) and a Catalyst 3750 at the other end. Users at the far-end connect to servers located at the data center over this fiber.

This connection has been working fine for the past 2 years, until a recent problem came up.

For two weeks now, the usual occurrence is for the fiber link to stop passing traffic while working until the 3750 is rebooted or the fiber connectors removed from the SFP port and replugged.

Meanwhile, the interface and line protocol remain UP on both switches during this abnormal behaviour. There are also no log messages occurring. Everything look fine on both switches. They just wouldnt pass traffic. The problem occurs about twice each day.

It's difficult diagnosing the problem now. I need help pls.

Regards,

Felix

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6 Replies 6

balajitvk
Level 4
Level 4

‎09-29-2007 10:56 AM

Hi,

I hope this link is Layer2 links with trunk enabled. If so, see whether any spanning tree blockings in that time.....

Rgs,

0 Helpful

felixnkansah
Level 1
Level 1
In response to balajitvk

‎09-29-2007 11:02 AM

Thanks.

The fact is, its a Layer 3 link (with IP addresses assigned to both ends of the connection).

During this period of abnormal behaviour, it is not possible to even PING the other ends however.

Regards

0 Helpful

balajitvk
Level 4
Level 4
In response to felixnkansah

‎09-29-2007 11:15 AM

Hi,

Which interface IP is not pingable 3750 or 6500??? Whether able to login thro. console on that time or not??? Sometimes spikes in the processor utiliztion may leave this effect for shorter duration.

Rgs

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felixnkansah
Level 1
Level 1
In response to balajitvk

‎09-29-2007 11:27 AM

HI,

I am not able to ping any of the interfaces from either switches. I mean there is no connectivity whatsoever from one end of the link to the other, even though line protocol remains up during this period.

I am able to console-in to the switches.

The fact is, when the problem occurs, the link never comes back on until we unplug and replug the connectors to the 3750 or 6509, or restart the 3750.

Regards

0 Helpful

balajitvk
Level 4
Level 4
In response to felixnkansah

‎09-29-2007 11:44 AM

Hi,

Could u paste the configuration on the both side switch ports???

Rgs,

0 Helpful

paul.matthews
Level 5
Level 5

‎09-29-2007 12:12 PM

Are the interface RX counters incrementing during the problem? What do the buffers look like? I presume CDP goes, but one way or both?

What versions of IOS?

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