Solve the problem that Linux cannot access the external network

Question:

A certain Linux server cannot ping the domain name, the following prompts:

Preparation ：

First make sure the router is connected and the router can access the external network. This can be confirmed by accessing the gateway.

[root@localhost ~]# ping 192.168.1.1
PING 192.168.1.1 (192.168.1.1) 56(84) bytes of data.
64 bytes from 192.168.1.1: icmp_seq=1 ttl=64 time=2.96 ms
64 bytes from 192.168.1.1: icmp_seq=2 ttl=64 time=1.75 ms

Free video tutorial sharing: linux video tutorial

If you are sure that there is no problem with the network, you can solve it through the following steps:

1 . Make sure the domain name server is set up. If not, it is recommended to set up Google's public DNS service. It should not cause problems.

[root@localhost ~]# cat /etc/resolv.conf
search localdomain

Because my DNS is not set up, pinging from the external network fails. Add dns to the file

[root@localhost ~]# vi /etc/resolv.conf
search localdomain
nameserver 202.98.96.68
nameserver 61.139.2.69
~

2. Make sure the gateway has been set

# grep GATEWAY /etc/sysconfig/network-scripts/ifcfg* 
/etc/sysconfig/network-scripts/ifcfg-eth0:GATEWAY=192.168.40.1

If not, add the gateway as follows:

# route add default gw 192.168.40.1

Or manually After writing the /etc/sysconfig/network-scripts/ifcfg* file, restart the network service:

# service network restart

3. Ensure that dns resolution is available

# grep hosts /etc/nsswitch.conf 
hosts:      files dns

If there is a problem with any of the above, correct it and test again , it should be no problem:

#ping -c 3 www.baidu.com 
PING www.a.shifen.com (220.181.6.175) 56(84) bytes of data. 
64 bytes from 220.181.6.175: icmp_seq=0 ttl=50 time=9.51 ms 
64 bytes from 220.181.6.175: icmp_seq=1 ttl=50 time=8.45 ms 
64 bytes from 220.181.6.175: icmp_seq=2 ttl=50 time=8.97 ms 
--- www.a.shifen.com ping statistics --- 
3 packets transmitted, 3 received, 0% packet loss, time 2002ms 
rtt min/avg/max/mdev = 8.450/8.977/9.511/0.446 ms, pipe 2

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