eth0 Link encap:Ethernet HWaddr 00:30:48:76:00:4E
If this is correct it means your computer is being used as dns-server. I believe you don't know what that means: In short, people use names computers use numbers. Every url you enter (like "/www.linuxquestions.org/") must be "translated" to an ip-adress. It's a bit like telephoning - to call Charles you need his number. Dns-servers are like big telephone books for internet.
Your internet-provider should have valid dns-servers for you, should be assigned automatically. It seems the computer is directly connected to internet, no home-router in between?
On cheap home-routers dns-forwarding often fails.
(I tried using 18.104.22.168 as dns-server, nothing resolved. It is not a dns server.)
- doesn't work, right?
In /etc/resolv.conf add as first line:
Now ping again. Does it work?
* If yes, you should be fine with that as your dns-server. However it's best to check with your isp what servers you are supposed to use.
* If not, reply back, with an exakt description of your network, how you connect to internet.