VoIP. when switching to a backup channel, registration flies. why?

Question

Telephony

Good afternoon colleagues.
History such when switching to a reserve channel the telephony does not work. and when switching back to the main channel, registration does not rise.
Inside the network, everything is fine, the call goes through. but outside, if you call, it says all the lines are busy.

Answer 1

You may need to clear the NAT translation table.
This was (as it is now - I don’t know) on Mikrotik, which, when the main channel fell, continued to send packets according to the old record to the same address.