Network Basic Commands Summary

Network Basic Commands Summary

set or modify hostname

a)     temporary ways

hostname NEW_HOSTNAME, but if you reboot your system, it will disabled.

b)    permanent ways:

edit “/etc/sysconfig/network” HOSTNAME, then restart system, it will effect..

And you better to modify the “/etc/hosts” to make the hostname be same as “/etc/sysconfig/network”, otherwise some service will start with slowly or error.

The picture is flowing:

View Network configuration

if you want to view the network configuration, you can use the command:

“ifconfig”

you also can view the network config

the detail of newwork.

If you want to add another network settings.
you use two ways flowing:

a)
temporary ways

use this
command:” ifconfig eth0:1 10.0.0.0/24 ”

or “ifconfig eth0:1 10.0.0.0 netmask
255.255.255.0”

if you restart
the network service ,it will be lost

if you want to
make it permanent, you should create a file whose content is same as “ifcfh-eth0”,
but file name is the network name you want to create.

modify or set DNS

DNS will be write two main files.

The first file is “/etc/sysconfig/network-scripts/ifcfg-eth0”

The second file is “/etc/resolv.conf”. But this
file is same as the above.

if edit the “/etc/resolv.conf” NAMESERVER, then
restart the network service, the NAMSEVER

will be lost and the DNS1 in the “/etc/sysconfig/network-scripts/ifcfg-eth0”
will be set in the “/etc/resolv.conf”. In a word, the “NAMESERVER” must keep
same with “DNS1

”

View route configuration

if want to view the route config ,you can
user the “route -n”.

the last line is default route.

you can also add new route or delete route.

add new route use this command

route
add default gw 10.0.0.254

delete existing route

route
del default gw 10.0.0.254.

Some ways to check you service whether can be used.

a)
ping

ping is mean send ICMP ECHO_REQUEST to network hosts

for example:

In
Windows Operate System, you also use this command.

b)
dig

dig means DNS lookup utility.

for example:

c)
traceroute

traceroute means to print the route packets trace network
host.

d)
tcpdump

tcpdump means to dump traffic on network.

if you want to check some requests and your service reply,
you can use this command.

for example:

First executing “tcpdump -n icmp -i eth0” in your Linux
System.

Executing “ ping 192.168.98.131” in Window Operate System DOS.

you will view those in Linux System

you can see the REQUEST and REPLY.

if a request is replied, this show you server is good.

if a request is not replied, show you server is error.

you can use this command to check you server whether error.

This is very useful commands!

How to check your server when it can’t go Internet

1)
checking physical line whether
fluent.

2)
checking your server IP,DNS and
route

3)
checking your server gateway

4)
ping open internet IP