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DHGmem
Beginner

Trunk link not connecting

I'm replacing a switch and I can't get the trunk link to the core connect.

 

I'm not 100% sure its not the fiber link to the core, but it was previously working and I traced it with a light pen. There are two available fiber links in this comm room and both don't work.

 

Config is pretty basic on both ends...

interface TenGigabitEthernetX/X/X
switchport
switchport mode trunk

 

Show interface on both ends...

GigabitEthernetX/X/X is down, line protocol is down (notconnect)
  ...
  Full-duplex, 1000Mb/s, media type is 1000BaseLH

I wanted a 10G-LR SFP but I thought it might be compatibility so i changed it back to the original 1G-LX SFP for now.

 

I've swapped out everything I could think of on both ends...

-Swapped the switch

-Swapped the SFP module

-LC/LC fiber - new out of the package

-Tried multiple SFP's (Same on both ends)

 

I also plugged the switch directly into the core via 10G-LR SFP LC/LC and it worked.

 

I don't know what else to try other than get someone to run a new fiber link which could be expensive.

 

Please help with some ideas to try

4 REPLIES 4
balaji.bandi
VIP Guru

Try setting speed 1G or try no autonegotiation interface command.

 

 

 

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Seb Rupik
VIP Advisor

Hi there,

Given your list of hardware checks, have you tried changing the polarity of the fibre at one end?

 

cheers,

Seb.

paul.driver
Beginner

Hello


@DHGmem wrote:

10G-LR SFP but I thought it might be compatibility so i changed it back to the original 1G-LX SFP for now
I also plugged the switch directly into the core via 10G-LR SFP LC/LC and it worked.


FYI - 10G will be Single mode, 1GB can be Single or Multimode
So check to see if you have a compatibility issue, also try crossing the TX/RX pins around

mlund
Rising star

Hi

You wrote " I traced it with a light pen", I have never seen that this is working on single mode fiber. I thought it only works for multimode.

And if your fiber is multimode, and the SFP:s are LX (single mode) that will be a problem. It can maybe work for a very short range with 10G, it reaches a bit longer with 1G, so the advice from @balaji to test with 1G is good. Or try with SX.

/Mikael