Trouble with SIP trunk registration

Hello,

I’m new to the forum but I have a bizarre problem that I would like to share.

my SIP trunk details are as follows:
sip_conf details:
[[51CA3-IC]
secret=password
type=user
context=from-trunk

[vpd1pbx1nlsbst02]
disallow=all
username=4034007207
type=peer
secret=xxx
insecure=invite
host=10.191.220.241
fromdomain=10.191.220.241
dtmfmode=inband
context=from-trunk
canreinvite=no
allow=ulaw

my sip_nat.conf is as follows:
nat=no
externip=10.191.220.241
externip=10.191.220.245
localnet=10.191.168.149/255.255.255.240
localnet=10.0.0.0/255.240.0.0

what is weird is that in the REGISTER being sent to the ISP, the 10.191.168.149 is the source IP even though it’s on a different physical interface. The trunk originally registers but the OPTIONS dialogue is only between the 10.191.220.241/30 interfaces where the 10.191.168.149 interface is expecting it. The trunk then goes offline and then eventually reregisters.

I’m suspecting there is a missing value in the sip_conf that will explicitly state that the SIP diagloge for this trunk it to originate from the IP that I’ve been assigned (10.191.220.242).

I think I found the issue.

Even though on the sip_nat.conf had the following configuration
nat=no
externip=10.191.220.241
externip=10.191.220.245
localnet=10.191.168.149/255.255.255.240
localnet=10.0.0.0/255.240.0.0

the peer setting was still able NAT via the other interface. By modifying the sip.conf with the following my registration is stable so far.
username=4034007207
type=peer
secret=123456
insecure=invite
host=10.191.220.241
fromdomain=10.191.220.241
dtmfmode=inband
disallow=all
context=from-trunk
canreinvite=no
allow=ulaw
nat=no