Andreas Granig writes:
UAC-1 sends a SIP-Register to SER-1, so NAT is opened for UAC-1 <-> SER-1. But since UAC-1 doesn't send something to SER-2, NAT is never opened between UAC-1 and SER-2, which is what I meant with "no NAT-binding". Because of this SER-2 can't send a SIP-Request to UAC-1 because it's blocked by the NAT-device.
yes, that indeed sounds like a problem. when contact of uac-1 is nated and memory only, ser-2 should use ser-1's address as source address for requests to uac-1. the other option might be to make ser-1 to send an options request to uac-1 using ser-2's address in contact.
perhaps somebody else has better suggestions?
-- juha