Intermittent reset of VoIP phones connected to Cisco 3750 switch stack

[mitchen]

We have 5 x Cisco 3750 (WS-C3750V2-24PS) switches running 12.2(50)SE1 stacked in a LAN in a new office.

A Mitel phone system is being implemented by a 3rd party on this LAN.   There is an intermittent problem where some of the phones will reset themselves (usually happens overnight and no obvious pattern to it – not all phones have been affected so far, for example). 

The phone system is maintained and managed by the 3rd party so we have limited visibility of how it is configured set-up etc (but we are responsible for the Cisco switches!) However, they say they are seeing errors on the Mitel kit along the lines of:

The CDP time-to-live data expired for DN: xxxxx
Check L2 switch configuration for potential problems.

They reckon this points to the problem being on the Cisco switches and have suggested that perhaps the switch is overloaded and is pulling some power to the ports.

However, we can see no power related errors in the Cisco switch logs whatsoever (and no CDP errors either)!   Also, as far as I'm aware, these switches are capable of supporting 15.4W of power to ALL 24 ports on the switch so power shouldn't be an issue?  The show interface command shows no errors or resets being reported on the switch ports and the show power inline command shows plenty power still available for allocation (also shows that 6.1W has been allocated to each connected phone, for what its worth)

So - basically, can anyone advise on a) what the problem could be and b)  how we can troubleshoot further on the Cisco side of things in order to pinpoint the cause of the problem?

The next suggestion we have been given is to try disabling CDP and enable LLDP instead so we are going to try that. (perhaps with CDP being a cisco proprietary protocol it doesn't interact so well with the Mitel devices?  Who knows!)

Any suggestions/troubleshooting advice would be most appreciated!

Thanks.

[mopauly]

I would not think CDP would attribute to any issues, but simply be ignored by the off brand phones.  Does Mitel supply any type of configuration guide or guidelines in regard to what they need to see on the switch from a config standpoint?  Can any debugging be done on the Mitel side to help pinpoint the cause?

[mitchen]

Hi Paul,

thanks for the reply.   Since it is a 3rd party that is installing the Mitel system for us, we have been very limited in what we can find out from them.  I know the Mitel phones are supposed to support CDP and, indeed, by and large they seem to work fine - apart from these seemingly random resets.  (Just for clarification, I don't mean the phones are from a 3rd party - the phone system and phones are all Mitel branded - its simply a 3rd party contractor installing it all for us, not Mitel themselves)

Much to my disappointment - we've been given nothing in the way of a configuration guide or what they need to see on the switches from a config standpoint unfortunately.  So we have simply configured the Cisco switches as per guidelines on CCO.  If any Mitel specific config is required, we have not been made aware of it! (And I've not found anything myself from a brief search of Mitel's website)

So basically I'm looking to find as much information as I can to troubleshoot this issue from the Cisco standpoint to try to either resolve it or pinpoint the cause (whether that turns out to be on the Cisco side of things or the Mitel side of things)

Would there be any advantage in disabling CDP on the switch and enabling LLDP instead?  Or is this likely to cause other issues?

Once again, suggestions welcome!

Thanks.

[paolo bevilacqua]

From where exactly the error message pops up?

From the phone? Are the phones running their latest firmware?

Is there a patter for this to happen ?Which exact IOS are your running on the switches ?

[mitchen]

The error message relating to the "CDP time-to-live data expired" and "Check L2 switch configuration for potential problems" comes from the Mitel system.  No such errors being seen on the Cisco side at all.  Indeed no signs of any problems that I can see on teh Cisco side of things at all so far!  I have been unable to correlate any of the problems with any events on the switches.

Seemingly no pattern to the problem - the symptoms being that the Mitel phones randomly reboot (tends to be overnight but I don't know if *only* overnight though I have requested more info)   I have also asked the question of our 3rd party installer as to whether a) the phones are all running the same firmware and b) whether they are running the latest firmware but haven't had an answer to this as yet. 

The switches are running 12.2(50)SE1 (/c3750-ipbasek9-mz.122-50.SE1)

[mopauly]

These links may be of assistance to you (if nothing more than a breakdown of the DP's):

http://www.cisco.com/en/US/technologies/tk652/tk701/technologies_white_paper0900aecd804cd46d.html

http://www.cisco.com/en/US/docs/switches/lan/catalyst3750/software/release/12.2_37_se/configuration/guide/swlldp.html

The last time I had an issue similar to this we ended up using wireshark and doing a packet capture at a network desktop endpoint to determine the cause of phones on a particular VLAN dropping and re-registering to our CUCM...but I am fortunate enough to work with a complete Cisco infrastructure from network to voice, and no third party products in between.

[mitchen]

Thanks, I'll take a look at those links you have provided.

Yes, my preference would have been for an all-Cisco infrastructure for data AND voice too - unfortunately it often comes down to cost and keeping the bean counters happy!  I think it also doesn't help having a 3rd party installing the phone system as we are reliant on them to provide information/diagnostics from their side and its in their interests to point the finger at the network switches that we have responsibility for rather than the kit that they have supplied and will be maintaining!   I would far rather we looked after it all ourselves but we don't have the neccesary voice skillsets required as yet so that ruled out that possibility!

[mopauly]

Hopefully that helps, I am not familiar with the Mitel products, and honestly would never have any desire to work with anything but Cisco The beauty of managing and delivering so many services through one wire to the desktop where everything plays well together is a nice benefit of being an all Cisco shop.

Unfortunately when you have multiple vendors involved this kind of issue can occur, and it's usually you as the customer who ends up having to pinpoint the problem even if it does not lie within your own configurations.