<-- SIP read from 192.168.1.26:5060: 
REGISTER sip:192.168.1.25 SIP/2.0
Via: SIP/2.0/UDP 192.168.1.26;branch=z9hG4bKadd87926e4694bfb
From: "grandstream1" <sip:601@192.168.1.25;user=phone>;tag=52efe48ae57b42ed
To: <sip:601@192.168.1.25;user=phone>
Contact: <sip:601@192.168.1.26;user=phone>
Call-ID: 66138cd71623361b@192.168.1.26
CSeq: 110 REGISTER
Expires: 3600
User-Agent: Grandstream BT100 1.0.5.18
Max-Forwards: 70
Allow: INVITE,ACK,CANCEL,BYE,NOTIFY,REFER,OPTIONS,INFO,SUBSCRIBE
Content-Length: 0


--- (12 headers 0 lines)---
Using latest REGISTER request as basis request
Sending to 192.168.1.26 : 5060 (NAT)
Transmitting (NAT) to 192.168.1.26:5060:
SIP/2.0 404 Not found
Via: SIP/2.0/UDP 192.168.1.26;branch=z9hG4bKadd87926e4694bfb;received=192.168.1.26
From: "grandstream1" <sip:601@192.168.1.25;user=phone>;tag=52efe48ae57b42ed
To: <sip:601@192.168.1.25;user=phone>;tag=as19f5dbdf
Call-ID: 66138cd71623361b@192.168.1.26
CSeq: 110 REGISTER
User-Agent: Asterisk PBX
Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, SUBSCRIBE, NOTIFY
Contact: <sip:601@192.168.1.25>
Content-Length: 0