Phones going offline

Every once in a while I have a phone that goes offline. The user doesn’t know it as they can make outgoing calls (internally or externally) but when someone calls their extension goes straight to voicemail. The fix is just to restart their phone.

The display on the phone shows no indication it’s offline.

Now, this morning, about half the staff member’s phones were offline. Restarting their phones fixed the problem but can anyone shed any light as to why this happens? At first I was thinking a POE switch had a hiccup but these phones are in different parts of the building and plugged in to different switches.

FreePBX 15
The phones are all YeaLink T42G

Sounds like you have a remote PBX and there are NAT and/or firewall issues where the phones are.

It’s all on-premise. No remote sites.

Then it is a networking issue. When a phone cant receive a call does it show Available in the PBX? Because if it is UNREACHABLE or UNAVAILABLE then the PBX cant talk to the phone.

Also remember, registers and invites (outbound calls) are not related. You can be unregistered which stops inbound but still make outbound.

In FreePBX, it shows it as being “offline.” However, on the phone display itself, there is no indication it’s offline. It’s still connected to the network.

The PBX isn’t talking with the phone properly. Registration is something that happens once during a period of time and is done again when that time expires. A phone will show registered if the initial registration was good. If you have keepalive active in the phone (phone pings PBX) if the pings stop the phone will show offline. If that is not enabled and the phone isn’t checking the connection, then the phone will show it is registered until it can’t again.

Rebooting the phone makes it register again to the PBX, then you can get inbound calls but after sometime if the PBX can’t qualify/keepalive the phone it will stop and mark the phone as unreachable (still tries)/unavailable (gave up)/offline (dropped the registration).

There is something happening in the network where A) the phone is not getting the keepalive/qualifies from the PBX or B) the PBX is not receiving the OK/ACK replies from the phone for the request it sent. Either of those point to networking issues. You’re going to need to run some packet captures so you can catch this and then review the PCAP to see where and when the communication fails.

I might want to add, it does sounds like an endpoint issue as a couple users have Clearly Anywhere and when their desk phone is offline, Clearly Anywhere appears to be working ok. So the problem doesn’t appear to be on the server.

I never said it was the server. I said it was a networking issue and since softphones on devices over wifi are working when the deskphones don’t points even more to a networking issue and one that involves your wired connections. So switches are good places to start, specially if it is a PoE switch. There could be power issues or other things happening.

Quick question, did you by chance add more deskphones or even other devices to the switch that draw off PoE? Because you have to look at the PoE power and what individual devices are drawing. If the switch has a 60W PoE power cap then you need to make sure all the devices in the switch are not drawing more than 60W overall. I’ve seen PoE switches with low power allotments being overdrawn on by a few devices that have a big draw.

No, absolutely nothing was changed or added to any of the switches. I don’t believe it’s a POE problem. As I mentioned earlier, the phones that went offline aren’t all connected to the same switch. There are 4 switches in the picture. Ultimately they do all connect to one switch in our computer room.

I believe the problem occurred yesterday, late afternoon after hearing some staff members say “I tried to call so and so and it just went to voicemail.” But we didn’t have anything go down and no power issues.

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