I am working as a technician in a telecom company, with main responsibility for supporting customers having problems related to VoIP.

Our customers use ATA's (adapters) between their routers and their analogue telephones. The problems occur when the ATA is trying to get through the router at UDP port 5060 (SIP). So you can say this is a NAT related problem. The customers therefore have to forward the right ports (mainly udp 5060-5063) in their routers, but this is not always so easy for our not always so technical customers. The result often being the customers can't get their phones to work.

What I need is a small application who I can use to scan which ports are open through a customer's router, when I know his IP adress. That way I can check wether the right ports are opened in the customer's router.

Anyone who can help me out here, who knows about a good application to do this job?

I preciate your replies.

Thank you.


Frode

Try this one:
http://www.insecure.org/nmap/