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check for open ports

Posted: Mon Aug 04, 2008 5:05 pm
by esannerud
Hello folks

I have a remote site that has an RB133 with os 3.9. Behind it are several machines that are remote controlled. I want to find open tcp ports on the machines behind the router.

Is there any way to do that from the terminal on the router? Or do I have to route all ports to the different machines and then do an nmap from external source?

Regards
Erlend

Re: check for open ports

Posted: Tue Aug 05, 2008 9:23 am
by normis
what do you mean by "open"? your router is a firewall, you can create rules that will stop all unwanted traffic from/to these machines. allow only certain types of traffic and block the rest.

Re: check for open ports

Posted: Tue Aug 05, 2008 12:33 pm
by esannerud
I know that the the router is the firewall. What I want is to check that the pc has the correct ports open on the local network. The only way I can do that is to route all tcp ports into the pc through the firewall and do an nmap from an linux box here. I do not want to do that since the pc then will be totally open to the internet.

What I would like is to do an portscanning from the firewall on to the local pc on the local network.

Reason for all this is that I can not get to the remote site just like that. Nor can I get other people to check it for me - in this case. And the only thing I can remote controll is the rb133. So I have very limited options here.

Erlend

Re: check for open ports

Posted: Tue Aug 05, 2008 10:54 pm
by crussell_1969
Don't open up all ports to any address; just open up all ports to the address of your linux box, do your port scan and than go back to your normal settings. Just be careful, if you setup the dst-nat to forward all ports to an internal pc, you won't be able to log in to the rb133 any longer. Make sure you keep ssh or telnet un-nat'd so you have a way to get back into the rb133.