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New Member

7945 IP Phone and Cisco 4506-E Switching "Issue"


Sorry for the abstract topic, but I'm not sure how to sum this up without a a running start :)


I have 3 sites with 4506-E switches working just fine with all existing phones. When I move 1 specific phone from Location 1, or 2 where it works fine to location 3 it only works for ~20 minutes before experiencing a plethora of issues. Sometimes it spins on "looking for IP" sometimes it just begins to drop massive amounts of packets(which also affects voice quality), and sometimes it just shows the default 2010 date stamp and a solid blue background.


Site 3 has 2 4506-E's and this happens on both of them, regardless of port. I've checked the phone and it's pulling an IP and it's in the correct Voice VLAN. The phone also works fine from my site 1 while on the same VLAN configurations. I've tested the phone in the exact same ports as presently working phones at site 3 to the same end.

Typically I can take any phone anywhere in my environment and have it work without issue.


I'm having a hard time narrowing this down to a phone issue when it works just fine... too a switch issue that is working fine with dozens of phones under the exact same configuration.

Ideas? Potential settings?

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Hall of Fame Super Gold

Ideas? Potential settings?

Ideas? Potential settings?

Your description is a classic example of a cable issue.  You can run a TDR (if it's supported on the line card).  


  1. Command:  test cable tdr interface <BLAH>;
  2. Wait for about 61 seconds (due to the limitation of the 4500 line card); 
  3. Command:  sh cable tdr interface <BLAH>; and 
  4. Post the output to #3.
New Member

 It doesn't look like my


It doesn't look like my Catalyst 4506-E's have the TDR Commands. Other ideas?

In the meantime I plan on bypassing the ports and testing the Phone directly off of Site 3's 4506. We are suspecting the distance as being too much for this specific phones "failing" interface. I expect this is what you are driving at with the Time-Domain Reflectometry test. I've never looked into TDR before, interesting stuff. :)


Site 1 and 2 are fairly small locations with shorter runs back to the MDF/IDF locations. The specific room we are in at Site 3 is a fairly long run, and as I said the phones presently in that room are working fine with the exception of this one.







Hall of Fame Super Gold

I've never looked into TDR

I've never looked into TDR before

Read THIS short blog.

It doesn't look like my Catalyst 4506-E's have the TDR Commands.

Do you have a switch with GigabitEthernet port, like a 3750G or a 2960G?  Anything to run an initial diagnostic?  It doesn't need to be PoE.

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