Fibre Madness!

[clockend25]

Thought I'd stick this up here and see if anyone has any suggestions because I'm firmly stumped.

 

A couple of weeks ago we re-cabled one of our network cabinets; completely stripped it bare and re-organised and cabled it. The fibre patch panel is interesting as it has a fibre connection from the core, but also has fibre runs from the core to two other blocks looping through it. I believe this setup is due to a change in location of the server room many years ago. So the patch panel is setup as follows:

 

1/2 (fibre from core) - ST/ST patch connected to 9/10 (fibre run to Block A)

11/12 - ST/SC patch into cabinet from core

5/6 (fibre from core)- ST/ST patch connected to 13/14 (fibre run to Block B)

 

The fun begins after we re-cabled the cab. The fibre patch leads were installed exactly as they were previously: the direct link back to the core for the cabinet was reestablished; the connection to Block B came back up immediately....Block A: nothing.

Balls.

 

Tried a plethora of different patch leads: nothing.

 

Tried the working patch lead from the Block B loop-through: nothing.

 

I then tested both sides of the loop-through to see if I could get any sort of connection either to the destination block or back to the core. Testing both sides of the loop-through with an ST/SC lead: both work.

 

Absolutely stumped by this. Having tested all of the above I'm not sure where the problem could lie given I've ascertained the fibre run is fine in both directions and tested the patch with several known good leads. At the moment I have connectivity restored via patching the link to Block A directly into a switch in the cabinet in question, however that isn't a long-term solution as it elongates an existing daisy-chain which could be a bit dubious once the network is used heavily again.

 

Any ideas greatly welcomed; we've looked at this for so long now that we're likely missing something incredibly obvious.

[snagrat]

I assumed you have changed the ends of the fibre patch lead around on one end only to ensure you Tx and Rx align correctly?

 

Or could be a mix match of fibre types. Can you confirm if both fibre runs are the same OM rating?

[clockend25]

Funnily enough while you posted that I've just ordered some patch leads of different ratings to test. I'll have a look tomorrow, thanks.

[LytchettNM]

I would try the suspect pair of fibres into another switch confirm to confirm that the link still works.

If it does it would suggest the sockets are possibly dirty reducing the amount of light?

If you have a spare pair of fibres from your core to this cabinet it might be worth trying this pair to.

When you say block A did not come up are you checking the GBIC for a link light or pinging something in the block?

[clockend25]

Both.

 

Also, I've tested the fibre directly into the switch and in both directions it works.

[LytchettNM]

OK so if the link light comes up then the problem is not a physical one, it would point to being a VLAN issue.

First think to check starting from the basics plug block a back in via the patch in the cabinet in the middle and check that you get a link light at both ends ie core switch and edge switch in block A.

Assuming the link light are up then check on the core switch which networks / VLAN's are being sent to block A, then go to block A and plug into the edge switch and check which networks / VLAN's it's configured for, I have know GBIC's lose connection if the fibre is broken so it won't harm to jack each GBIC and then reseat double checking then link lights come back up at both ends.

[LytchettNM]

Also if you core to edge network is routed you will need to make sure you have the have the gateway setup, I know you have said it was all working before you disconnected everything in the cabinet but to fault find you need to double check all the basics, and just asking have you reboots both the core switch and the edge switch in block A?

[fiberoptics]

Great. By the way, where did you purchase the patch leads of different ratings to test?

[clockend25]

Comms Express.

[fiberoptics]

Here are also some for you to consider if you need cheaper ones in the future. Custom & OEM Multimode Fiber Patch Cables | FS.COM

[clockend25]

Right, so having tried every rating of ST/ST patch lead still nothing. Saw VLANs mentioned above but we're a flat network so that's a no-go as well.

 

[cpjitservices]

Have you checked the connections into fiber patch panel haven come loose for Block A ? Break in the fiber maybe ?

[Michael]

Two thoughts come to mind -

 

Did you take a picture of all Fibre Patch Panels before disconnecting?

 

The fact the link works with an ST/SC and not a native ST/ST as before, at least this demonstrates you're using the correct OM cable type (whatever that may be).

 

It's easy to get ST/ST wrong, simply because the cable will fit both ways. I can't see what else the issue may be to be honest.

[Michael]

Also you could try criss-crossing cables in this experiment -

 

Try 1/2 to 13/14 and 5/6 to 9/10.