I have had this problem in three offices starting in 2013. And it just happened to me today in an overseas office. This problem can remain hidden in your telephone system for years and not be a problem because it’s so rare for a phone to get assigned a new IP address via DHCP.
Basically, a phone reboots for some reason. When it comes back up, there’s no dialtone. Or, if you have more than one gateway, you might get intermittent dialtone.
In my network, these items were also true:
- The gateway and the phones are on the same subnet
- The phone was assigned a different IP address when it rebooted (this may not be obvious since you don’t always know the phone’s previous IP address)
If you have more than one gateway, the problem might seen intermittent. you can “list trace station” and watch the phone pull dialtone:
12:19:49 G711A ss:off ps:20 rgn:1 [10.9.10.90]:39798 rgn:1 [10.9.10.3]:2094
That IP address on the third line – that’s the gateway assigned to serve dialtone for this call. In my case, I have a gateway in the local office, and a gateway in the datacenter. Whenever the user said “hey, there’s no dialtone!”, it had drawn a resource from the local gateway in the same subnet. The phone worked in all other ways – there was just no media.
There are MILLIONS of Avaya forum postings regarding no dialtone, one-way audio, etc. In my case here, the problem was caused by the arp cache in the G450 gateway. That’s pretty obscure. The IP address changed, but the MAC address in the arp cache did not change. So the gateway is trying to feed dialtone to the wrong MAC address.
The fix was simple: log into the G450 and issue these commands:
- ‘no ip arp inspection‘ (this disables arp caching)
- ‘clear arp-cache‘ (this clears the arp-cache, which sounds scary but will not affect service)
- ‘copy run start‘ (this will write the settings to flash memory to survive a reboot)
That fixed the issue of no dialtone. It did not fix the issue of phones rebooting and getting different IP addresses though. I will write a different post for that, since it was a completely unrelated issue.
I hope this helps! Please let me know if this works for you.