In this post, I brought up the command ifconfig and I promised to talk about the output. It is rather confusing, so let’s pull it apart bit by bit so we can understand that ifconfig output.

eth0      Link encap:Ethernet  HWaddr 00:1A:2B:3C:00:00
          inet addr:192.168.0.10  Bcast:192.168.0.255  Mask:255.255.255.0
          inet6 addr: fd91:ae3b:d5e8:aa85:0:0:0:0 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:41620 errors:0 dropped:0 overruns:0 frame:0
          TX packets:40231 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:21601203 (20.6 MiB)  TX bytes:6145876 (5.8 MiB)
          Interrupt:21 Base address:0xe000

Let’s begin at the beginning! The first line says

eth0      Link encap:Ethernet  HWaddr 00:1A:2B:3C:00:00

That means that the link is an ethernet link. There is an ethernet cable attached to this computer connecting it to the Internet. The next part of the line says HWaddr and has some letters and numbers after it. We talked about IP addresses before and those can change on your computer. If you have a laptop and take it to a coffee shop, you’ll get a different IP address from the one you’ll have at home or that you would get in a library. Your computer never knows what IP address is going to show up, it isn’t like your home address which never changes.

The HWaddr is the fixed address of your computer, like your home address. It doesn’t change, no matter what. It’s also known as the MAC address. It’s set by the manufacturer of your ethernet card and never changes, no matter where you take your computer. You could take it to the Triskelion and it wouldn’t change.

Oh wait, that got destroyed in Captain America: Winter Soldier, didn’t it. You can’t take it there, but you could take it to the North Pole and it wouldn’t change.

The next line:

net addr:192.168.0.10  Bcast:192.168.0.255  Mask:255.255.255.0

Is information about your IP address and we already discussed that. Next time, we’ll talk about the line that starts with ip6. This ifconfig output is extensive, isn’t it? Lots of information that tell us all about the network interface on the computer.