How to find IP from MAC address?

Question

In other words I have a MAC address and I want to find the user's ip address. In my routers config page I can see 3 MACs on the DHCP list. One is my desktop and the other one is my laptop. I would like to find out what/who the other one is.

Answer 1

Sounds like you're trying to track down a freeloader.  Since DHCP is the mechanism that assigns IP addresses to requesting computers (and other computer-like devices), getting their IP address won't help you find them.  If you want to get rid of them, follow these steps:

Because routers differ as to details, I can't be specific about how to accomplish these steps, but they're almost all done from within the router's administration web pages. Note: It’s best to do them from a computer cabled (even just temporarily) to the router rather than wirelessly, especially since wireless administration will be deactivated by step #1.

1. Deactivate wireless access to your router's administration web pages so only a computer connected via an Ethernet cable can reach them.  This won’t affect wireless use of the Internet, just wireless administration. Even if you don’t want to leave a computer connected via a cable, leave the cable there for when you need it.  Here are some horror stories of people who didn't:

http://answers.yahoo.com/question/index?...

http://answers.yahoo.com/question/index?...

2. Turn off the SSID (network name) broadcast from the router.  There's no need to advertise your network's presence.  You're not running a hotspot; everyone who should be on your network should know its name.

3. Change your SSID from the default.  Hackers know that routers come with default SSIDs and look for them.

4. Set up encryption with an encryption key.  The longer, the better. WPA (if your network and all your computers can support 802.11G) is better than WEP.  WEP is better than nothing.

5. Limit access to only the computers you want on the network via MAC filtering. (MAC refers to unique NIC (Network Interface Card) addresses, not Macintosh computers, and not IP addresses.)  This isn't a defense against hardcore freeloaders -- it's possible to fake MAC addresses -- but it keeps out casual interlopers.

6. Change the range of and/or limited the number of automatically assigned IP addresses (DHCP) to reduce the chance of extra users.  Again, hackers know what ranges routers come from the factory with.  Changing them makes it a little harder to hop on board.

That should get rid of your interloper.

Hope that helps.

Answer 2

the IP address would be located in the DHCP lease list that is on your router.  its is very important that you find what computer is registered on your network but knowing the IP it has is pretty much useless (see Unauthorized DHCP Clients http://en.wikipedia.org/wiki/Dhcp#Securi... step one is to check the hard lines connected in your network. from what i hear of your setup there should be one cord from your modem to your router, then one cord to your desktop, as well as a wireless setup for your laptop(this is a guess). make sure all cord going connected to your network are thing you trust. if you do indeed have a wireless setup, make sure you have a password on it so people from across the street don't use it(like i used to).if these measures don't help try blacklisting the mac address in your routers security settings(if this causes a device to lose network connectivity then you found the origin of the mac addy).

final notes- all devices on the internet need an ip address and therefor a mac address(real or virtual) so check if you have devices that qualify

-game consoles

-additional network cards.

-etc

email me if you need more help.

Answer 3

The IP assigned to that MAC will be on the DHCP list on your router. Alternatively, if it's on the same network as you, send out a broadcast packet (ping your broadcast address) then check your own ARP table (arp -a), this will display all MAC to IP associations.

Answer 4

Computers can determine IP addresses from MAC addresses using DHCP (and formerly other protocols like RARP and InARP).

There is no universal mechanism for an end user to determine an IP address given a known MAC address, although it can be done in certain specific situations.