Debug Register Failed

I’m sorry for asking for help here, but I’m trying to support about 20 phones that were moved from office to home due to this whole corona thing.

It has worked surprisingly well, but I have some phones that have intermittent failure during registration. They will work for a a day or so, but then (usually in the morning it seems), the phone will show “no service”. I get a call or an email asking for help and when I connect to the phone, it looks fully configured, but it just keeps failing to register.

Does anyone have tips for where I can look for logfiles to debug failed registration either on the handest or on the PBX/SIP server?

I’m using FreePBX hosted at

Current Asterisk Version: 13.29.2

The phones are Yealink T27-G

Happy to pull and post any info necessary, but really looking for tips on how to figure out where the failure is and why.

Thanks in advance!


Does a reboot of the phone get things working again temporarily? If so, you may want to check the registration interval/expiration on the phones and try a lower setting, like 2 minutes. Also, are the ip’s of the phones changing at all? It would just help to know in case it’s some kind of firewall issue.

When you say they are failing to register, what are you seeing? Do you see incoming registration requests that are not going through the full handshake? Or do you stop seeing the requests on the pbx? If you’re not familiar with viewing sip packets, you can do this from the asterisk command line with ‘pjsip set logger host’(assuming it’s a pjsip extension), then reboot the phone or wait until the packets come in. Another option is to run ‘sngrep’ from the system command line and watch for packets that way. You can take a look at the transaction that happens with a successful registration, and compare it with a failing one, assuming you get any packets at all.

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