What should I do if I can’t access the external network under centos?

Problem description:

This centos server on the intranet has always been fine before, but suddenly it cannot access the external network. It appears that the intranet is OK. Access the resources of this computer, but cannot access the external network on this server.

[root@localhost ~]# arp -n
Address                  HWtype  HWaddress           Flags Mask            Iface
192.168.1.102            ether   e4:9a:79:d8:bf:0d   C                     eth0
192.168.1.214            ether   40:8d:5c:21:00:1a   C                     eth0
192.168.1.111            ether   4c:8d:79:e4:aa:d0   C                     eth0
192.168.1.1              ether   00:17:16:08:3d:6a   CM                    eth0
[root@localhost ~]#

Troubleshooting:

It is not a DNS problem or an IP conflict problem. It is caused by the gateway's network card address.

(Recommended tutorial: centos tutorial)

Solution:

Update the network card address, first find the network card address that can access the external network, such as Execute arp -a in current WIN to get the network card address.

D:\mysite>arp -a

接口: 192.168.1.204 --- 0xc
  Internet 地址         物理地址              类型
  192.168.1.1           00-17-16-08-33-6a     动态
  192.168.1.3           94-de-80-55-1b-8d     动态
  239.255.255.250       01-00-5e-70-ff-fa     静态
  255.255.255.255       ff-ff-ff-ff-ff-ff     静态

D:\mysite>

Execute the following command on centos:

# 在 Centos 上先执行删除旧的网卡信息
/sbin/arp -d 192.168.1.1

# 重新设置新的，上面win里面找到的 网卡，横线改为冒号 
/sbin/arp -s 192.168.1.1 00:17:16:08:33:6a

Test:

[root@localhost ~]# ping www.baidu.com
PING www.a.shifen.com (183.232.231.172) 56(84) bytes of data.
64 bytes from 183.232.231.172: icmp_seq=1 ttl=55 time=9.03 ms
64 bytes from 183.232.231.172: icmp_seq=2 ttl=55 time=8.80 ms
64 bytes from 183.232.231.172: icmp_seq=3 ttl=55 time=10.1 ms
64 bytes from 183.232.231.172: icmp_seq=4 ttl=55 time=108 ms
^C
--- www.a.shifen.com ping statistics ---
4 packets transmitted, 4 received, 0% packet loss, time 3814ms
rtt min/avg/max/mdev = 8.804/34.058/108.239/42.831 ms
You have new mail in /var/spool/mail/root
[root@localhost ~]#

Perfect solution!

Recommended related video tutorials: linux video tutorial

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