Curious problem with fibre lnk

[Kevin Dorrell]

I have a curious problem with a fibre uplink between an access layer 4503E (S8) and a distribution layer (4500X).

Up to now, the access switches have been 4500 S2+ with a pair of 1 Gbps SX uplinks.  That has been working fine.  Now I upgrade the access switches to 4503E S8 with a pair of 10 Gbps SR uplinks.  Most of the access switches worked fine without any problems.  But on one of the access switches, one of the link will not come up. I can see the light both ways down the fibre.  The SR transceivers tell me the RxPower is about -4 dB in each direction, just like all the other access switches.  But only one link comes up.

If I take the faulty link out of the VSS port-channel, substitute 1 Gbps SX transceivers, and bring it up as an STP standby link, it works perfectly.  Change the transceivers to 10 Gbps SR, and the link does not come up.  The light gets through fine at about -4 dB.  The configurations of the two links are identical.

Has anyone else experienced something like this?

Kevin Dorrell

Luxembourg

[Reza Sharifi]

Hi Kevin,

Have you tried replacing the SFP+ and also the actual port on the 4500x?  We had problems with some of our 2960x switches where the 10Gig uplinks from 2960x switches to VSS (4500x) would no come up, but not sure about 4503 with 4500x. A reboot of the access switch would fix things temperately, but a few days later the problem would reappear. The permanent solution was to replace the 2960x with 3650s.

HTH