TroubleShooting network

This article describes what you can do if you have network problems. We will first identify the problem and then solve it.

Do you have an IP address

Find out if you have an IP address

ip addr

If you do not have an IP address, fix this problem before proceeding.

We assume your IP address is 192.168.0.2

Can you reach your computer

Find out if you can reach your own computer

ping 192.168.0.2

Do you have a standard gateway

If you can ping all computers in your network but not any computer in the internet you probably don't have a gateway configured. Find out with the command route like this:

# route
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
192.168.0.0     *               255.255.255.0   U     0      0        0 eth1
link-local      *               255.255.0.0     U     0      0        0 eth1
loopback        *               255.0.0.0       U     0      0        0 lo
default         192.168.0.1     0.0.0.0         UG    0      0        0 eth1

The first blue line means: If there is any IP package for an IP address 192.168.0.*, just send it over network device eth1. The second blue line means: Every IP package that has not been handled yet, send over network device eth1 to the default gateway 192.168.0.1.

See also

• TroubleShooting
• NetWork
• TroubleShooting Sound
• iptraf
• ethtool
• nmap
• telnet
• netstat