Well heres the thing... I'm pretty well versed in concepts of hacking inside a network, but I've begun testing in senarios were a router is acting as a firewall, and I am outside the network. really have no clue how to get past it or to get any info.

Given that I have an IP, how is it possible to get an idea of the network topology, or at least contact to any system inside the network. If you guys have any info or links to documentation, I would really apriciate it.

Things I'm interested in:

Acessing specific machines from outside a router/firewall

Possibly ways to enumerate or attack a router (in order to penetrate the network)

Viewing network topology from outside a router


Any help would be greatly apriciated