08-12-2014 01:14 PM - edited 03-16-2019 11:43 PM
Hello! Today we noticed that if trying to run tdr cable test on catalyst 2960s on port with plugged 3905 IP phone we always getting results like that:
Interface Speed Local pair Pair length Remote pair Pair status
--------- ----- ---------- ------------------ ----------- --------------------
Gi1/0/19 100M Pair A 67 +/- 0 meters N/A Normal
Pair B 68 +/- 0 meters N/A Normal
Pair C 69 +/- 1 meters N/A Short
Pair D 68 +/- 1 meters N/A Short
Is it ok or not? Another phone models have all normal pair in same port.
08-12-2014 03:12 PM
Interface Speed Local pair Pair length Remote pair Pair status --------- ----- ---------- ------------------ ----------- -------------------- Gi1/0/19 100M Pair A 67 +/- 0 meters N/A Normal Pair B 68 +/- 0 meters N/A Normal Pair C 69 +/- 1 meters N/A Short Pair D 68 +/- 1 meters N/A Short
Read this: How to use Time-Domain Reflectometer (TDR)
Pair C controls PoE. Because there's a "short" at around 68-69 (cable) metres from the switch, it means your device won't power up.
Pair D controls GigabitEthernet. Because there's a "short" at around 68-69 (cable) metres from the switch, it means your device won't be able to operate and/or negotiate at GigabitEthernet.
This is indicative of a cable problem. The cable is most likely to be the one that's cabled up to the phone.
08-13-2014 02:03 AM
Thanks for your reply! We thought about cable problem and tried to change cable but nothing helps. And moreover - all our 3905 phones on any ports and any cable give this error...
08-13-2014 03:13 AM
Take the phone and plug directly into the switchport. If the phone works, then your issue could be the following:
1. The remote end patch port; and
2. The remote end patch cable
08-13-2014 05:03 AM
> Take the phone and plug directly into the switchport. If the phone works, then your issue could be the following:
Did it already, error is the same but phone is working regardless it plugged directly or not. So is it normal beaviour for thie phone model or not?
08-13-2014 05:36 AM
Hmmmm ... What is the IOS version of your switch?
08-13-2014 08:18 AM
Switch Ports Model SW Version SW Image
------ ----- ----- ---------- ----------
* 1 28 WS-C2960S-24PS-L 12.2(55)SE7 C2960S-UNIVERSALK9-M
08-13-2014 03:21 PM
For 2960S, upgrade your IOS to 12.2(55)SE9 or 15.0(2)SE4.
I remembered seeing an IOS in the early 15.0(2)SE where the TDR result gets "stuck" and you'll need to reboot the entire chassis just to reset the result.
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