simon.schönbeck.dk

Tag: MAC

  • Static ARP Ubiquiti EdgeOS

    There are times when one needs to reach a certain device on the network and cannot as multiple devices have the same IP address. This should in theory not happen but it does in networks where people can freely connect devices themselves. If the device has a static IP address which another device already has, it is nearly impossible to reach it to reconfigure it remotely as packets would end up on the wrong device. This where a static ARP entry can smooth out things forcing the router to only send packets to that single device of one’s choice

    sudo arp -s 192.168.0.1 e4:ea:b4:08:a8:32 -i eth1

    This tells the router that “192.168.0.1” is at MAC “e4:ea:b4:08:a8:32” and will stop it broadcasting ARP requests; it just sends packets directly to that MAC.

    When done simply delete it again:

    sudo arp -d 192.168.0.1 -i eth1


    After that, the router will go back to the normal ARP behaviour of broadcasting ARP requests instead of using the fixed MAC.

    If you run show arp eth1 after deletion, you should see the static entry removed.

  • Find a Windows Vista MAC Address

    Yesterday eve I had to add a laptop to my network which is using MAC address filtering. The laptop ran Windows Vista and I tried to locate its MAC address by using the good old ipconfig within a command prompt. This gave no results as apparently the network details only get listed once an actual network connection is made. As you probably have realised this is a catch-22 situation as without the MAC address registered on the router I was never going to make a network connection in the first place…!

    Actually the weird thing is that the MAC address is normally on a sticker on the bottom of laptops, but in this case there was no such sticker.

    Google as in most other cases provided a quick fix by pointing me in the right direction. There is a command specifically for this task named funnily enough: getmac.