Hi guys. I tried to configure a NAT on my PC, so I used iptables to configured some IP translations.
After reboot my internet is completely gone. The interesting facets are:

1. I have IP from the router.
2. I can ping the router.
3. I can ping other PCs connected with the router.

But when I ping 8.8.8.8 or www.google.com it shows "network is unreachable"

Then I tried to clean all the iptables configurations, reboot, still not working.

How can I fix this? I thought even I made huge mistakes on iptables configuration if I cleared all the settings it should back to normal?

Your problem is not iptables, which you should restore to a good set of firewall rules. You have lost your default route. Issue the command "route -n" to be sure.