[Serusers] SIP Invite request coming on the Source port of Register request

[mahesh]

Hi All,

To be more specific on the problem, I am using the following network 
configuration.

       HOST1 XP---FW/NAT---Internet---HOST2 XP

Network Configuraton:
Host1's IP address : 172.16.4.8
FW Internal address: 172.16.4.1
FW external address: 202.125.84.163
Host2's IP address : 202.125.84.164
SER(public server) : 195.37.77.99

FW/NAT has SIP-ALG implementation.
SJPhone is installed on both Host1 and Host2. Now Host1 registers with the 
SIP proxy server.
The register request after the NAT(ALG) process has the src port of 
55001(IP:202.125.84.163) and
the contact port of 60002(IP:202.125.84.163). Similarly SJphone on Host2 is 
also registered with
the proxy server. Now when a call is made to Host1 from Host2 using 
SJPhone, the SIP invite
request coming from Host2 is sent to the proxy server, which in turn is 
sending it to
202.125.84.163 on port 55001(source port of register). This request is 
supposed to come on port
60002(contact port of register).

A month back when i tested in the same configuration, the request from the 
external machine was coming on the contact port of the register 
request(according to the RFC 3261). But when i tested it yesterday it was 
having the mentioned problem behavior. Could someone please let me know if 
anything is changed in the proxy server(SER) which is causing this 
behavior. Also how this behavior can be avoided.

Thanks in advance.

Best Regards
Mahesh