How to get *internet* IP?

Question

Imagine a situation, I have PC with two lan cards, one is connected to internet another is connected to local network, how can I detect IP which is connected to internet wi

Answer 1

The internet connection must be on the same IP network as the default gateway.

There's really foolproof no way to tell from the IP address if you can reach the "internet" or not. Basically you can communicate with your own IP network. Everything else has to go through a gateway. So if you can't see the gateway, you're confined to the local IP network.

The gateway, however, depends on other gateways, so even if you can access the gateway, you may not be able to reach some other network. This can be due to e.g. filtering or lack of routes to the desired networks.

Actually, it makes little sense to talk about the internet in this sense, as you will probably never be able to reach the entire internet at any given moment. Therefore, find out what you need to be able to reach and verify connectivity for that network.