Irregular Network Drops - Various Users


I have had several users across our network experience a random network drop on our UCM6510 phone system, including myself. There doesn’t seem to be any real pattern to this, although there are several users that have this happen more often and some none at all. I personally did not set up this network nor phone system and I am fairly certain that the firmware is not up to the latest version. These phones are using PoE and do not lose power during the incident, just the network. The network goes down with a spinning loader on the screen for a few moments until a connection is re-established. At first we thought this was isolated to a specific user, but have found this is not the case. I have made some attempts to troubleshoot this through cabling and devices with no avail. There are only network drops with the phones and not our computers. If anyone has any ideas please help me out! I have a pretty good feeling updating the firmware could help resolve this, but my manager is not quite as confidant with that being the issue.




Spencer, is this happening on Internal and External calls, or only on External ones?


OKay Spencer, heres a quick realisation for you - it is possibly happening with the computers as well, data is less reliant and deals with packet loss, SIP doesn’t (Phones)

There could be many reasons for the issue and I would start running a packet capture over the network because it sounds like either their is congestion over the network which could point to a network switch failing, a faulty patch lead, something creating a broadcast storm at the time the phones start to cease operating. Now you said it is random ports, when was the last time the Network switches were powered completely off and turned on after a minute?
This clears the mac cache on the switch and usually fixes up erroneous random glitches on a network.

Are the Network Switches smart switches?
Are the phones on their own Network switch?
Is there a VLan for the Telephones?
Is this using a Gigabit network?
What is the DHCP server?
When was the last time the Network fly Leads or Patch leads changed?
Is it a cat 5, cat 5e, cat6, cat6a, cat7 environment?
Has any other server/device been introduced to the network around the same time things went haywire?

A few questions for you to run with… the simple thing of turning off the network switch might be the easiest task to perform.




If you want someone to hop in and take a look at the network and settings let me know. I have resources available that can handle this to give you a better idea of what may be happening.


A network trace would prob be the best place to start ! Do you see devices dropping more than others ? Would LOVE to see a trace of this !


@merlin02131 just to make sure I understand, you would do the trace on the UCM via a network capture?


I would !

I would try and see what the network is doing to drop and re auth the call(s) .

Not sure if the ports are trying to auto config and dropping or its a network issue like dropping packets causing the devices to re authorize …
Could be hardware
Could be traffic related

hard to tell by the description !

I saw some dell switches just recently dropping packets and they could not figure it out ( Dell that is ) .

ScottsIP makes some valid points …