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.
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.