Identifying MAC addresses on your network
July 7, 2013 4:25 PM   Subscribe

So I used to have a router running Tomato firmware, which would show me the MAC addresses of every machine connected to the router. I have since switched to a faster ROSEWILL| RNX-N300RT router, but cannot locate the MAC addresses of connected machines. Is there a good, free utility for OS X or Windows 7 that will show me the MAC addresses of connected machines?

The weird thing is that the Rosewill router admin page puts a little Tomato icon in the URL bar. I have been unable to successfully flash it with Tomato, however.

I need the MAC addresses so I can conveniently limit my childrens' access to the internet, in a technocratic, passive-aggressive way, as opposed to doing any actual parenting.
posted by craniac to Computers & Internet (7 answers total) 1 user marked this as a favorite
apparently your router is supported by dd-wrt, which should let you block by mac address.
posted by at 4:40 PM on July 7, 2013

Zenmap, the GUI front-end for nmap, will do this. It will run on any platform.

Your target should be your local subnet, expressed as a CIDR range. So, if your router's IP address is, you would enter as your target.

Zenmap will then scan every IP address in that range and return information about the hosts that it finds. "Quick scan plus" mode will return MAC addresses, among other things.

RE: icon weirdness, most likely the Rosewill has the same IP address that the old Tomato router did, but doesn't provide its own favicon. Your browser is pulling up the Tomato favicon from cache.
posted by zjacreman at 4:50 PM on July 7, 2013 [1 favorite]

When you say you cannot locate the MAC addresses on your network, are you looking in the right places? Under the "Wireless->Wireless Statistics" menu you should be able to see it, or under "DHCP->DHCP Clients List". If they're not there, it's probably because they aren't set up with the SSID (network name)/password you have set up on the new router. Once they authenticate on the new network they should be visible.

If there's something wrong with the router that prevents it from showing the active clients (your children's computers are on and connected, right?), you could try this in a terminal window:
arp -a

That should work for OS X or Windows, although for OS X you might have to try "sudo ping" for the first command. This assumes you haven't changed the default address on the router, but if you did that you should be able to figure out the new broadcast address on your own.
posted by five toed sloth at 4:55 PM on July 7, 2013 [3 favorites]

Response by poster: Thanks all. The statistics section of my router admin page shows the mac addresses, albeit sans the machine name.

I tried installing DD-WRT and almost bricked the router. I also read there were throughput problems with this router. I am looking forward to playing with Zenmap. Thanks for the multiple, useful solutions.
posted by craniac at 5:07 PM on July 7, 2013

Rosewill router admin page puts a little Tomato icon in the URL ba

Just a note here, your browser will cache favicons sometimes. Assuming both routers were its not that the Rosewill is running Tomato its just a cached favicon.

Actually right now my icon for Ask Mefi is BT Internet (long story)
posted by bitdamaged at 6:00 PM on July 7, 2013

If you are looking for the mac addresses of the machines themselves, all the operating systems should have a way to identify them. On Windows open a command prompt, then run ipconfig /all. On Mac googling suggests system preferences -> network. Although I'd have probably have gone for a cmd line utility that might be "ifconfig -a" which is linux, but i cant get access to an osx box at the moment.
posted by TheAdamist at 6:41 PM on July 7, 2013

Came here only to congratulate you on the last paragraph. Nicely done. Brought a smile to my face.
posted by nostrada at 8:14 PM on July 7, 2013

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