I have a IP web cam on a LAN which connects to an ADSL router and it is possible to connect to the internet. The ADSL router can obtain an IP from ISP automatically when it is switched on. The cam has its own predefined local IP address. I can view the images on the LAN in a web browser, just typing in the IP address of that cam. But I'd like to know how can I connect to it remotely over the internet. Many thanks.

All you need to do is to find out the TCP/UDP port number that camera works on and map that port to a virtual server port on your router. From outside you will be directly connected to that port on your camera. Hope this helps.

Thanks for your tips. I have added the port number to the virtual server configuration. Then I tried to type the IP allocated by the ISP on a browser. It asked me the username and password. But I didn't know what to put in. What do I do in order to get in?

what you have done it accessed the login for your router. What you need to do is when accessing the Webcam type the IP:Port Example(VNC)ISP leased ip address is 123.22.34.221 the port i want to use is 5900. If i was going to access this i would use the IP address of 123.22.34.221:5900 basically looks like this (ISP leased IP x.x.x.x):(webcam port number)