Remote client unable to register with ser after enabling port forwarding from ext public ip to internal asterisk private address.

Following is my setup:

 

SER listens on port 5060 on public ip xx.xx.xx.xx (ext NIC eth0)

Asterisk listens on 5060 on internal private ip 192.168.1.4 (int NIC eth1)

Following port ranges are forwarded from xx.xx.xx.xx to 192.168.1.4:

SIP 5004-5082, RTP 10001-20000.

Once I stop port forwarding, there is no problem with remote client registration.

I’m an absolute newbie. I’ve googled and searched through the ser users archives for prior similar issues without any luck.

Help is highly appreciated.

 

Iddris