Only 1 port does not support speed 1g connection on C2960G switch.

[masoowo]

Hi,

A web server is connected to C2960G switch port G0/35 with speed a-100 and duplex a-full
even the web server has a NIC card which supports 10/100/1000G.

Thus, I forced the setting of speed 1000 and duplex full in the Switch port G0/35 and the web server's NIC card, but the link is not up anymore.

So i took an action as below to figure out this issue.
(SW Model: WS-C2960G-48TC-L // version: 12.2(35)SE5)
(Switch port configuration: speed auto, duplex auto / Server's NIC card configuration: speed auto, duplex auto)

  - Changed the UTP cable -> The symptom was still the same.

  - Connected Laptop to the same port(G0/35) -> The link was connected with speed a-100 and duplex a-full 
                                                                              even the laptop's NIC card supports 10/100/1000G

                                                                              (forced Speed 1000, Duplex full on the both devices: The link was not up anymore)

  - Connected the web server's NIC card to another port on the same switch -> The link was connected with speed a-1000 and duplex a-full.

The port works as normal with speed 100 and full. It makes me feel confused if it is really the physical hardware problem or there is another caused reason logically.

So has anyone experienced this kind of situation? 

Thank you,

Dennis

[Leo Laohoo]

Thus, I forced the setting of speed 1000 and duplex full in the Switch port G0/35 and the web server's NIC card, but the link is not up anymore.

I bet if a TDR is enabled on the port the result will show, at least, Pair D as being OPEN or SHORT.  

[masoowo]

Thank Leo Laohoo for your reply.

As i mentioned above, I connected the server to another port with the same UTP cable to another port G0/34 instead of G0/35 on the same switch(C2960G) and the connection was speed a-1000 and duplex a-full. 

As a result, I assume that it is not the physical UTP cable problem. So is there other root cause for this issue?

Thanks again

Dennis

[Leo Laohoo]

As a result, I assume that it is not the physical UTP cable problem.

Unfortunately, I disagree.  I will make the conclusion until I see the TDR result.

[masoowo]

Okay Leo. 

Once i get the TDR result, I will update it here.

Thank you very much!

[masoowo]

Hello Leo,

This is the TDR result on the SW as below.

--------------------------------------------------------------------------------------------

prb3#show cable-diagnostics tdr interface g0/35

TDR test last run on: August 27 05:56:31

Interface Speed Local pair Pair length        Remote pair Pair status

--------- ----- ---------- ------------------ ----------- --------------------

Gi0/35    100M  Pair A     3    +/- 4  meters Pair B      Normal             

                Pair B     5    +/- 4  meters Pair A      Normal             

                Pair C     5    +/- 4  meters Pair C      Normal             

                Pair D     5    +/- 4  meters Pair D      Normal              

--------------------------------------------------------------------------------------------

Please, help me to analyse this result.

Thank you in advance.

[Leo Laohoo]

TDR result shows all clear.  

The NIC card is negotiating to 100 Mbps and the cable is cable of supporting 1 Gbps.  

[masoowo]

Thank you so much for your help. 

When i connected the server to another port on the SW without modification, The connection was speed a-1000 and duplex a-full.

In addition, I connected my laptop to the G0/35 port and the connection was speed a-100 and duplex a-100, but when i connected my laptop to another port on SW, the connection was speed a-1000 and duplex a-full.

Actually, It is my first time to meet this result so that i want to verify what things makes this result for the negotiation of the connection between the SW and the Server.

Please, tell me your opinion Leo if you have.

Thank you again.

[Leo Laohoo]

Maybe Gi0/35 port interface has "speed 100" configured?

[masoowo]

Unfortunately, The configuration of speed is auto on port g0/35.

[Leo Laohoo]

Maybe upgrade the IOS of the switch?

[masoowo]

Well, I will consider it and try to convince my customer.

By the way, Is it possible that only 1 port physically has a problem like this?

Have you heard or had a similar problem like me before?

[Leo Laohoo]

Never seen a behaviour like this before.

[masoowo]

Okay. I think I know what to do and tell to my customer now.

Thank you so much for your kindness and help.

Always take care and Have a nice day Leo!