Phones won't work occasionally

[Jatinderpal]

3CX phone system installed in one of our offices worked fine for 6-7 months before an issue of phones just not working popped up. We have Watchguard T35 firewall and phone network is on VLAN completely separate from the data network. Our firewall auto restarts daily at 3am. Once nearly every 15-20 days the phones just wont work. To make them work, we restart Firewall then these start working. There is no configuration changes in the Firewall since last 6-7 months so not sure what is happening now leading to this issue. Any help/suggestion in this regard will be highly appreciated. Thanks.

 

[Evolute IT]

Did the Watchguard firmware got updated?

Also, if you are Hosted on 3CX (unless you're in the wrong forum), STUN is not supported. So they won't help. Too much of a headache.

Have you tried using an SBC?

 

[Jatinderpal]

Thanks Frederick for you quick response. Yes we are hosted on 3CX. I'll check with my provider about SBC.

 

[Kevin@voxtelesys]

Does the watchguard have SIP ALG disabled? Can you put a trace up and see if any packets are blocked?

I don't think 3CX allows root access otherwise you could monitor with SNGREP and see if there are any issues when the phones drop.

 

[JohnS_3CX]

The fact that they start working when you restart the firewall may be pointing towards an issue with your firewall. At least this is a good place to start looking.

You can verify this by checking the traffic when the problem starts again:

- Run a capture on the PBX
- Run a capture on the phone UI
- Try to make a call to say voicemail or to another internal extension

When the call fails, open the captures and see if the phone attempted to REGISTER or send an INVITE message, and then also see the PBX capture to see if those SIP messages arrived. If they don't then you can be quite certain that the firewall (or something in the network) stops the traffic.

By the way, you can also run a capture on the firewall itself, and I suspect you will see the phones sending the messages, but the firewall not forwarding them to your PBX

 

[Jatinderpal]

Thank you Kevin & John for your suggestions. I'll surely try these out. Thanks again.