I have four 5000 series PBXs. One of them has a situation where random and intermittent (the two most hated words in the world) IP phones will lose connection with the PBX. Unplugging/plugging in the phone will reconnect the phone to the PBX. The phones are on different network switches and it doesn't seem to be a recurring issue with specific phones. It changes. Does anyone have an explanation as to why this may occur?
Are you using POE switches? When it happens, are there any errors on the switch port that it's connected to?
We are using Mitel power supplies at each phone. No errors are found in PBX or network logs. It's as if they just decide to stop communicating.
So, it's not like they're losing power from the Mitel power supplies, as the phone would reboot and 'probably' reconnect when done.
Does the phone go to a state where it's got a blinking cursor (that's the best way I can describe it)?
Are the phones with issues connecting to the same 5000 pbx? Are there any issues on the switch that the pbx connects to? I'm guessing you may be looking at a problem with the network port on the switch or pbx at this point. Is it possible to port mirror the switch port for the pbx and run a sniffer on it?
Our network guy has found that the will try once to get an IP address. These are in a DHCP Reservation table. If they do not get the address, they will not try again. There is just a single attempt.
Has there been anything introduced into the network lately that could be causing issues with DHCP?
What device/server/etc is providing DHCP for the phones?
How long are your DHCP leases for?
If memory serves correctly, a DHCP client should a renew request when 50% of the lease has expired. If it doesn't get an offer, then it should continue trying until the lease expires.
The 8600 series phones all have DHCP reservations. We had to do this in order to group all of the phones together. We have network scanning software that disables the 8600s if touched. This allows us to enter an IP range to ignore.
Interestingly, the 5300s are unaffected by the scanning software.
I'll throw another dart at the board...
Do you have more than one DHCP server? If so, are the reservations entered on both DHCP servers?
What type of device/server is providing the DHCP services?
From what you have said, if a device stops responding, unplugging/replugging it will get it active again. It seems as if the phones sometimes do not get a response when re-requesting a DHCP lease after a period of time. What are your DHCP lease times set for?
2 weeks. This does not happen to all devices. I have four IP phones at my desk (one for each PBX), and I can't remember the last time it happened to one of them.
What type of servers are running DHCP services?
My boss would have a field day with the side of my head if I started giving out that information.
