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Cisco 7821 and Asterisk

Hi guys,

we have a lot of Cisco 7821 with firmware SIP78xx.12-5-1SR2-2 configured and working with Asterisk.

Sometimes some phone deregisters and does not re-register itself.

Theese are our template conf for registration:




Any idea how to improve these configurations or understand the problem?

Because same environment other phone brands we have no problem and not all Cisco phones have this problem.


VIP Expert

check all the Devices has same Version of code running.


Enable some debug on Asterisk see why this is failing. ( how are you resolving this issue ?) - Hope all your NTP Settings ok here ?


Can you post fill template XML file or refer below template for reference :


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Yes, all devices have same version.

We had no error on log but we didn't enable sip debug during problem.

We solved with a phones reboot via ssh.

We have configured xml following link that you posted we have same tags for registration, expire time, retry etc.

Leo Laohoo
VIP Community Legend

You have multiple phone models (and not just 7821)?

Yes, multiple phones are Cisco 7821 and also we have Snom and Yealink registered on the same Asterisk server. Not all Cisco 7821 phones have problem.
Leo Laohoo
VIP Community Legend

When the phones deregister, do they reboot?

No, we made a manual reboot via ssh

Leo Laohoo
VIP Community Legend

So the phones deregisters and you have to reboot the phones in order for it to register back again.
If this is the case, then I am suspecting this is a firmware bug.

you have not confirmed other phones have - same model and same firmware ? please confirm



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