Re: discovering a service behind a nated network

[Tim Hanekamp <thanekamp () gmail com>]

To check if the service is up just attempt to telnet to the ip on
whatever port the service would be running on.  Using netcat will give
you a better detailed report of what is happening during the telnet
session, but even using the normalt telnet function IF the service is
alive it will establish a connection and just sit and wait.  Once you
get this connection, you now know that the problem is not whether the
service is running, but whether it is working properly.

Alternatively, you could use nmap or some other port scanning program
to scna the IP and determine what services are open on that box.  Hope
that helps.


On Fri, 10 Sep 2004 23:23:54 +1200, Hayden Searle
<hayden.searle () safecom co nz> wrote:
> I agree with Jason that Nagios is a good way to monitor the web servers,
> or you could talk them into some BigIP F5's which load balance, monitor
> and report on services.
>
> As for the port forwarding, well it depends on what the gateway device
> is. If it's a firewall then I would get the dept that look after it to
> SSH onto the firewall and try to access the server from there, if that
> works then it could be the translation on the gateway device not working
> properly. Most devices should be able to tell you if the translation is
> working through the logs, but in the end it really comes down to what
> the device is and what logging is setup for the connections. They need
> to give some more info before you could answer that. The simple way out
> would be "Call the other department and have them check the gateway
> device"
>
> Regards
>
> Hayden Searle
> Network Security Specialist
>
> -----Original Message-----
> From: linux user [mailto:linuxteam () gmail com]
> Sent: Sunday, 5 September 2004 12:55 a.m.
> To: security-basics () securityfocus com
> Subject: discovering a service behind a nated network
>
> Hiya All,
>
> 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?
>
> The reason i am asking this is because i have been asked that
> question on a job interview, and i did  not know what the correct
> answer was, it was related to a web cluster farm then.
>
> 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
> can use ssh to
> the gateway server, but then that is run by a different dept. and you
> have no access to that.
>
> sorry if my English langauge is a bit rusty
>
> TIA
>
> Anst
>
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a certified computer examiner, learn to recover trace data left behind by
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