Detecting Computers Using Router with static IPs

bbimber · Post by **bbimber** » Wed Feb 09, 2005 9:03 pm

I have a linksys wrt54g. I have a number of computers connecting to it, and one of them was set up with a static IP. The rest of the computers appear in the DHCP table, but anything with a static IP will not. Just out of curiosity, is there another way to view what static IP computers are connecting to my router and what their IPs are?

bbimber · Post by **bbimber** » Wed Feb 09, 2005 9:10 pm

I have a second part to this question: Is it possible to set up my computer to automatically detect the IP address, and have the router automatically assign it a set IP based on the MAC address?

Tekmazter · Post by **Tekmazter** » Thu Feb 10, 2005 9:44 am

First, with the router the only way I could think you could do this is to look at your traffic log. You need to turn on logging first. Once you do that, you'll be able to see some traffic but I'm not sure if it will show what IP Address going out that it's coming from.

The easiest and probably best method to do what you're looking for is to run a port scan of a range of IP Addresses. Download NMap and run a scan of your entire network range. You don't need to do all 64000 ports, just do a range scan of only a couple. You should get some hits unless of course the person has a firewall of their own in place that just drops packets. Anyway, this should point you in the right direction.

Post by **YeOldeStonecat** » Thu Feb 10, 2005 9:50 am

Scanners like Angry IP Scanner, set to scour your 192.168.1.XXX range.

I'm guessing you're looking at finding "freeloaders" who are on your network. Introduce MAC filtering on your router, enter the MACs of computers you only wish to allow onto the network. Stop freeloaders in the first place.

Tekmazter · Post by **Tekmazter** » Thu Feb 10, 2005 10:43 am

YeOldeStonecat wrote:Scanners like Angry IP Scanner, set to scour your 192.168.1.XXX range.

I'm guessing you're looking at finding "freeloaders" who are on your network. Introduce MAC filtering on your router, enter the MACs of computers you only wish to allow onto the network. Stop freeloaders in the first place.

Expanding upon YeOldeStonecat, you might also disable the beacon on your WAP, although this isn't fullproof. Anyone who know's what they're doing can still find it, but this will sqaush the newb's who think they're being cool by leaching onto your AP. Also, of course employ WEP and change it periodically. Even disabling DHCP is a good idea as well.

Checklist:

Change Admin PW on AP
Disable DHCP
Disable Beacon
Change default network IP range if possible.
Deploy WEP
Enable MAC filtering

That should lose a few freeloaders.