RE: discovering a service behind a nated network

["Mike" <mike () superiorholidayadventures ca>]

> I would like to discover if a service that is behind a NATed network
> is still working, for
> example if a web server is in a private network, Nated behind a
> gateway, how could i from an external network check if the server is
> down/ or there are network problems between the server and the
> gateway? is there a way to use a tool such as traceroute for
> NATed/Firewalled network from an external link?

You can telnet into most ports and see if there's a banner served.  If
it's specifically a webserver you're testing you could issue the command
"GET / HTTP/1.0", or issue the appropriate HTTP 1.1 commands.  You could
also just point a web browser at the IP or domain name.  Doing the above
should tell you if the service is up behind the NAT box.

If it's a network issue between the client and the server, your typical
network troubleshooting commands are your best friend
(tracert/traceroute, ping).

You may also end up diagnosing possible DNS problems.


> another reason is howto troubleshoot a service that has been port
> forwarded from
> the gateway, the port forwarding works for other services, but this
> specific service is not reachable, and you can not tell whether the
NATed
> box
> was down, or the route was down, or what, you could debate that you

Well, if the same box forwards other ports but does not forward a
specific port, or that specific port/service no longer works, I would
say that it is *not* a problem with the NAT box and rather a problem
with the destined host.

Hope that helps,

Mike Fetherston

---------------------------------------------------------------------------
Computer Forensics Training at the InfoSec Institute. All of our class sizes
are guaranteed to be 12 students or less to facilitate one-on-one
interaction with one of our expert instructors. Gain the in-demand skills of
a certified computer examiner, learn to recover trace data left behind by
fraud, theft, and cybercrime perpetrators. Discover the source of computer
crime and abuse so that it never happens again.

http://www.infosecinstitute.com/courses/computer_forensics_training.html
----------------------------------------------------------------------------