I have asterisk behind DD-WRT v24-sp1STD (of coz in DMZ).
When I try connect from LAN it's work everything good, but for example from office, I haven't sound and in asterisk console I see:
WARNING chan_sip.c: Maximum retries exceeded on transmission SDsijfa01-07dc74ef8e566c8772759c25 104f5fba-ao4gh00 for seqno 939791693 (Critical Response)
WARNING chan_sip.c: Hanging up call SDsijfa01-07dc74ef8e566c8772759c25 104f5fba-ao4gh00 - no reply to our critical packet.
I think is problem with NAT or something, but maybe someone have a solution. Other services on server work correct. But asterisk no :(