POE 2960S ports come up for some workstations but no others

the-lebowski · ‎05-06-2013

Weird issue with a POE 2960 running 15.0(2)SE2.

What I am seeing is some laptops can connect to a port and get a DHCP address fine, others get no link light whatsoever. IE if I plug my laptop into port 41 I get link light and a DHCP address. If another user plugs into that port he gets no link light and the port will not come up. If I plug the same cable (jack) into the users laptop sitting beside the user in question the port comes up.

Also if that same user plugs into the back of his phone (different vlan and different switch) he gets a DHCP lease without fail, albeit on a seperate vlan (phone is plugged into an avaya IP office). So the issue seems to be with his laptop and the cisco 2960s.

nterface GigabitEthernet1/0/41

switchport access vlan 26

switchport mode access

switchport voice vlan 34

power inline auto max 15400

srr-queue bandwidth share 1 30 35 5

queue-set 2

priority-queue out

mls qos trust device cisco-phone

mls qos trust cos

auto qos voip cisco-phone

spanning-tree portfast

service-policy input AUTOQOS-SRND4-CISCOPHONE-POLICY

end

Any ideas?

Leo Laohoo · ‎05-06-2013

Any ideas?

Run a TDR on the ports not working. Post the "sh cable tdr interface " if you are unsure.

Steve Fuller · ‎05-06-2013

Presumably you've checked the obvious things such as matching speed and duplex i.e., this isn't hard coded such that auto-negotiation is disabled on the users laptop?

Regards

the-lebowski · ‎05-06-2013

Users laptops were all sent to auto negotiation. If i connected to the user directly to the switch the port came up so auto neg worked directly on the switch. I then hardcoded his laptop to 100mb/full and connected it back to the jack at his desk and it worked.

So some cross talk or wires crossed on the patch? This happened to two users and I had to hardcode both of them.

Leo Laohoo · ‎05-06-2013

I then hardcoded his laptop to 100mb/full and connected it back to the jack at his desk and it worked.

Let me guess ... This is a 1 Gbps client? If this is a 1 Gbps client but will only work in 100 Mbps, then I strongly recommend you run a TDR. Instructions are easy to follow.

the-lebowski · ‎05-06-2013

Yeah 1gbps clients. What I don't understand is if it was a cable issue why would one laptop be able to negotiate but another not be able to?

I will run the TDR tests and post the results.

the-lebowski · ‎05-06-2013

And the port in question:

nterface Speed Local pair Pair length Remote pair Pair status

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

Gi1/0/41 100M Pair A 50 +/- 0 meters Pair B Normal

Pair B 52 +/- 1 meters Pair A Short/Crosstalk

Pair C 52 +/- 1 meters Pair C Short/Crosstalk

Pair D 51 +/- 1 meters Pair D Open

sw1-2960#show cable-diagnostics tdr int gi1/0/40

I went even as far as switching the cables, and the patches and everyone I connected to this particular laptop showed the same results. A normal laptop shows this:

Interface Speed Local pair Pair length Remote pair Pair status

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

Gi1/0/40 100M Pair A 53 +/- 0 meters Pair B Normal

Pair B 52 +/- 0 meters Pair A Normal

Pair C 53 +/- 0 meters Pair C Normal

Pair D 52 +/- 0 meters Pair D Normal

sw1-2960#show cable-diagnostics tdr int gi1/0/40

TDR test last run on: May 06 16:52:36

So it must be the client as the same port works fine on my laptops.

Leo Laohoo · ‎05-06-2013

Wow. Port Gi 1/0/41 has one of the dirtiest patch cables I've ever seen. The fault is the cable nearest the PC/Laptop. Replace that and see if the client negotiates to 1 Gbps. If not, then re-run the test.

PS: I hope your switch is not running 15.0(2)SE1 if you plan to re-run the TDR.

the-lebowski · ‎05-07-2013

Thanks, using 15.0(2)SE2.

I just realized the test above was two different ports. I re-ran the same tests using the same cable and same interface on the switch:

Users laptop:

Interface Speed Local pair Pair length Remote pair Pair status

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

Gi1/0/40 100M Pair A 50 +/- 0 meters Pair B Normal

Pair B 51 +/- 0 meters Pair A Normal

Pair C 52 +/- 1 meters Pair C Open

Pair D 51 +/- 0 meters Pair D Normal

My laptop:

Interface Speed Local pair Pair length Remote pair Pair status

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

Gi1/0/40 auto Pair A 52 +/- 0 meters Pair A Normal

Pair B 52 +/- 0 meters Pair B Normal

Pair C 52 +/- 0 meters Pair C Normal

Pair D 51 +/- 0 meters Pair D Normal

sw1-2960-be#

Which leads me to believe its the users laptop, because mine auto negotiates to 1000 and his only a 100.

Leo Laohoo · ‎05-07-2013

Yes. It's possible. But no it's not.

Look at the label under "Remote Pair". Look at the first one, it's says cross-over and the second one says straight-through.

Next, look at the status. First one has an Open circuit in Pair C but it's all Normal in the second test.

Try the following:

1. Replace the patch cable nearest the laptops and try again;

2. Try another patch PORT nearest the laptops and try again (the patch port COULD also be potentially faulty); and

3. Directly connecting both laptops to the switchports and try again.

the-lebowski · ‎05-10-2013

I did all of that and reduced everything to the same port/cable/patch and different laptops. THe only problem appeared to be when the user connected his laptop. My laptop had no issue (older thinkpad vs my MAC).

And to answer your questions:

1. Same results

2. Same results

3. His laptop could connect fine directly to the switch

I am just going to chalk this up to the users laptop.

I am no longer onsite and have no way of testing anymore.

Thanks for your help though.