"Network is unreachable" when attempting to ping google, but internal addresses work

Question

I can get to other PCs in my house on the 192 network, but trying to go outside gives me the "network is unreachable" message. p3p1 is up with a good IP Address. Running Fedora 16. What should I do next to troubleshoot?

All other PCs in the house are working (Windows, Mac).

Answer 1

You say all other pcs in your house have a connection. Then the problem lies only with your linux machine. There are several possibilities:

1. You do have a connection, but you cannot reach your DNS; you can diagnose this by

   ping -c1 8.8.4.4
   

   if you can reach Google, then you have a connection, and you only need to update your DNS servers. Edit (as sudo) your /etc/resolv.conf file and add these two lines:

   nameserver 8.8.8.8
   nameserver 8.8.4.4
   

   and now you are good to go.

2. You cannot ping Google, but you can ping your router, or any other pc in your LAN. In this case case, it is possible that you also have problem 1, so you will have to check for that, but first, you need to check your routing table. Print it with

   ip route show default
   

   and check that there is a reply, like this one:

   default via 192.168.11.1 dev wlan0 proto dhcp metric 600
   

   (this is for my laptop). What is important is that the correct IP address of your router is shown exactly where mine (192.168.11.1) is shown. If an incorrect IP address is shown, or, worse, if the ip route show default command receives no reply, then your routing table has been corrupted. You may simply restore it by means of:

   sudo ip route del default (only if the wrong IP address appears)
   sudo ip route add default via IP.address.OfYour.Router
   

   and now we may go step 1.

3. If you cannot ping any pc on your LAN, then there is another kind of problem, and more questions will need to be asked. But we'll cross that bridge when we get there.