3750X-12S-E strange problem

[merima_ccna]

Hello,

we have 3 stack L3 switches (3750X-24T + 3750X-12S) in a core of the network (I will refer to them as S, T and Z), interconnected in an optical ring over DWDM. All 3 stacks are working with no problems for 3 years, without being reloaded. A few days ago, I reloaded T stack, but after that, connection between S and T stack stopped working, and whatever I tried with optical ports didn't help.

Also, yesterday, we planned to connect one of the branch offices to Z stack, and the same thing happened. 

Interesting behavior is that the other side is sensing optical signal and blinking. There is even output packets in "sh int" command, but "sh int" command of the 3750X-12S port shows down/down and 0 packets input and output. More weird is that I see laser from the SX SFP inserted in a 3750X-12S port.

I tried changing SFP, changing SFP slot, shut/no shut of the port doesn't help.

Did anyone have this problem?

I would like to try everything before reload and upgrade, because these stacks are core L3 switches.

Currently working IOS is c3750e-universalk9-mz.150-2.SE2.

Thanks,

Merima

[Liang Duo Guo]

I had the same issue with 3750X-12S switch, I use 3750x-12S as distribution switches with many 3750X-48P switch stacks on it, All worked for a long time until one day I reloaded one of access 3750X-48P stack, the ports on 3750x-12S didn't come up and  no matter to shut/no shut, replace SFP, fiber etc, the ports didn't come up. I had to reload it to bring them up, originally I thought it was IOS related as I am running 12.2(55)SE5, but you have the same issue with 15.0.2SE2. if there is a bug, it must exist on many IOS codes or it is a hardware issue.

[merima_ccna]

Did you upgrade 3750x-12S, or you are still using 12.2(55)SE5?

Did it happen with your switches ever again?

I am a bit scared of reload because it's a core switch aggregating many other branch offices and I have no backup hardware if anything goes wrong :/

Thanks for you reply!