Cannot SSH my home PC

Question

I am attemtping to SSH my home PC from another PC. Before I even get to the command line, I need to know my IP address. But I'm getting confused. If I use ifconfig, I get a a load of "inet" numbers for eth0. If I go onto any of the dozens of "test your IP" websites they all point to an address that is actually the address of my ISP. So what should I use when I want to use SSH?

I'm using Linux.

Answer 1

The address you get from the "test your ip" websites is your public IP address. This is the address that makes you unique on the internet. Most likely, this address is assigned to your router. The IP addresses of your computers, laptops, etc are internal IP addresses, unique to your network, not the internet.

If you want to SSH to your home computer from another location, you need your public IP address and to enable port forwarding on your router (port 22 for SSH) to your PCs internal address. Check your router's manual on how to do this.

Be aware that your public IP, assigned by your ISP, is most likely assigned by DHCP. This means that the IP address could change without notice, although not likely.

Answer 2

So, ifconfig from a linux command line, will give you some of the info you need:

eth0      Link encap:Ethernet  HWaddr 00:e0:52:90:a0:6e  
          inet addr:192.168.100.4  Bcast:192.168.100.255  Mask:255.255.255.0
          inet6 addr: fe80::2e0:52ff:fe90:a06e/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:2739429 errors:0 dropped:0 overruns:0 frame:0
          TX packets:95275 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:1104760995 (1.1 GB)  TX bytes:7946649 (7.9 MB)
          Interrupt:17 Base address:0x8c00 

The eth0 is your first ethernet adapter [likely your only adapter]. The second line under that shows inet addr [my example shows 192.168.100.4]. Yours will likely be 192.168.1.x if you are using one of the more popular home routers to share your internet connection. If you want to connect to this computer from another computer at home, this is the ip address you should use. If you want to connect to this machine from the internet, you need to configure your router to map port 22 to this ip address [192.168.1.x in my example]. Either way, if you are going to routinely ssh into the machine, you should set up a static ip address for it, either by a DHCP Lease reservation, or configuring a static ip address in the machine itself. If you configure static ip in the machine, make sure it is outside of the range that your router uses for dhcp leases.