Linux-Centos 7 网络NAT连接模式不能上网问题排查

Linux-Centos 7 网络NAT连接模式不能上网问题排查

首先启动centos系统后，检查ping www.baidu.com 无法解析，后转root用户
[normal4@localhost ~]$ ping www.baidu.com
ping: www.baidu.com: 未知的名称或服务
[normal4@localhost ~]$ su -
密码：
上一次登录：三 6月 17 09:16:40 CST 2020pts/0 上
[root@localhost ~]# whoami
root
[root@localhost ~]#

1、检查网卡信息！！！

[root@localhost ~]# ifconfig
lo: flags=73<UP,LOOPBACK,RUNNING>  mtu 65536
inet 127.0.0.1  netmask 255.0.0.0
inet6 ::1  prefixlen 128  scopeid 0x10<host>
loop  txqueuelen 1000  (Local Loopback)
RX packets 2631  bytes 1059258 (1.0 MiB)
RX errors 0  dropped 0  overruns 0  frame 0
TX packets 2631  bytes 1059258 (1.0 MiB)
TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

irbr0: flags=4099<UP,BROADCAST,MULTICAST>  mtu 1500
inet 192.168.122.1  netmask 255.255.255.0  broadcast 192.168.122.255
ether 52:54:00:7d:79:7c  txqueuelen 1000  (Ethernet)
RX packets 0  bytes 0 (0.0 B)
RX errors 0  dropped 0  overruns 0  frame 0
TX packets 0  bytes 0 (0.0 B)
TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0
[root@localhost ~]# ifconfig -a
ens33: flags=4098<BROADCAST,MULTICAST>  mtu 1500
ether 00:0c:29:e4:67:a0  txqueuelen 1000  (Ethernet)
RX packets 0  bytes 0 (0.0 B)
RX errors 0  dropped 0  overruns 0  frame 0
TX packets 0  bytes 0 (0.0 B)
TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

lo: flags=73<UP,LOOPBACK,RUNNING>  mtu 65536
inet 127.0.0.1  netmask 255.0.0.0
inet6 ::1  prefixlen 128  scopeid 0x10<host>
loop  txqueuelen 1000  (Local Loopback)
RX packets 8008  bytes 3303986 (3.1 MiB)
RX errors 0  dropped 0  overruns 0  frame 0
TX packets 8008  bytes 3303986 (3.1 MiB)
TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

virbr0: flags=4099<UP,BROADCAST,MULTICAST>  mtu 1500
inet 192.168.122.1  netmask 255.255.255.0  broadcast 192.168.122.255
ether 52:54:00:7d:79:7c  txqueuelen 1000  (Ethernet)
RX packets 0  bytes 0 (0.0 B)
RX errors 0  dropped 0  overruns 0  frame 0
TX packets 0  bytes 0 (0.0 B)
TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

virbr0-nic: flags=4098<BROADCAST,MULTICAST>  mtu 1500
ether 52:54:00:7d:79:7c  txqueuelen 1000  (Ethernet)
RX packets 0  bytes 0 (0.0 B)
RX errors 0  dropped 0  overruns 0  frame 0
TX packets 0  bytes 0 (0.0 B)
TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

root@localhost ~]#

2、发现有个网卡没有启动！！！
PS.后期发现可以直接跳到第4步执行命令，也可以解决问题（即不需要手动启动网卡）

**先启动网卡**
[root@localhost ~]#ifconfig ens33 up
**检查网卡启动是否成功**
[root@localhost ~]#ifconfig

ens33:flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
inet6 fe80::20c:29ff:fee4:67a0  prefixlen 64 scopeid 0x20<link>
ether 00:0c:29:e4:67:a0  txqueuelen 1000  (Ethernet)
RX packets 1  bytes 60 (60.0 B)
RX errors 0  dropped 0 overruns 0  frame 0
TX packets 7  bytes 586 (586.0 B)
TX errors 0  dropped 0 overruns 0  carrier 0 collisions 0

lo:flags=73<UP,LOOPBACK,RUNNING>  mtu65536
inet 127.0.0.1  netmask 255.0.0.0
inet6 ::1 prefixlen 128  scopeid0x10<host>
loop txqueuelen 1000  (Local Loopback)
RX packets 12452  bytes 5263410 (5.0 MiB)
RX errors 0  dropped 0 overruns 0  frame 0
TX packets 12452  bytes 5263410 (5.0 MiB)
TX errors 0  dropped 0 overruns 0  carrier 0 collisions 0

virbr0:flags=4099<UP,BROADCAST,MULTICAST> mtu 1500
inet 192.168.122.1  netmask 255.255.255.0  broadcast192.168.122.255
ether 52:54:00:7d:79:7c  txqueuelen 1000  (Ethernet)
RX packets 0 bytes 0 (0.0 B)
RX errors 0  dropped 0 overruns 0  frame 0
TX packets 0  bytes 0 (0.0 B)
TX errors 0  dropped 0 overruns 0  carrier 0 collisions 0
[root@localhost ~]#

3、网卡已经启动，但未分配到IP地址！！！

**重启network服务**
t@localhost ~]# service network restart
Restarting network (via systemctl):  Job for network.service failed because the control process exited with error code. See "systemctl status network.service" and "journalctl -xe" for details.
[失败]
[root@localhost ~]#

4、服务启动失败，猜测可能是NetworkManager服务导致，需要关闭它！！！

[root@localhost ~]# systemctl stop NetworkManager
**同时需要重启network服务**
[root@localhost ~]# service network restart
Restarting network (via systemctl):                        [  确定  ]
[root@localhost ~]#

5、再次检查网卡信息！！！

[root@localhost ~]# ifconfig
ens33: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
inet 192.168.208.130  netmask 255.255.255.0  broadcast 192.168.208.255
inet6 fe80::20c:29ff:fee4:67a0  prefixlen 64  scopeid 0x20<link>
ether 00:0c:29:e4:67:a0  txqueuelen 1000  (Ethernet)
RX packets 471  bytes 30148 (29.4 KiB)
RX errors 0  dropped 0  overruns 0  frame 0
TX packets 32  bytes 4889 (4.7 KiB)
TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

lo: flags=73<UP,LOOPBACK,RUNNING>  mtu 65536
inet 127.0.0.1  netmask 255.0.0.0
inet6 ::1  prefixlen 128  scopeid 0x10<host>
loop  txqueuelen 1000  (Local Loopback)
RX packets 41368  bytes 17635554 (16.8 MiB)
RX errors 0  dropped 0  overruns 0  frame 0
TX packets 41368  bytes 17635554 (16.8 MiB)
TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

virbr0: flags=4099<UP,BROADCAST,MULTICAST>  mtu 1500
inet 192.168.122.1  netmask 255.255.255.0  broadcast 192.168.122.255
ether 52:54:00:7d:79:7c  txqueuelen 1000  (Ethernet)
RX packets 0  bytes 0 (0.0 B)
RX errors 0  dropped 0  overruns 0  frame 0
TX packets 0  bytes 0 (0.0 B)
TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

[root@localhost ~]#

6、上面的命令我们已经看到IPv4的地址了，检测下是否能正常联网！！！

[root@localhost ~]# ping -c 3 www.baidu.com
PING www.a.shifen.com (180.101.49.11) 56(84) bytes of data.
64 bytes from 180.101.49.11 (180.101.49.11): icmp_seq=1 ttl=128 time=18.3 ms
64 bytes from 180.101.49.11 (180.101.49.11): icmp_seq=2 ttl=128 time=17.7 ms
64 bytes from 180.101.49.11 (180.101.49.11): icmp_seq=3 ttl=128 time=20.5 ms

--- www.a.shifen.com ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2004ms
rtt min/avg/max/mdev = 17.726/18.854/20.511/1.207 ms
[root@localhost ~]#

7、如果当你下次重启虚拟机的时候，还是发现网卡没启动，那么就永久关闭NetworkManager服务！！！

[root@localhost ~]# systemctl disable NetworkManager
Removed symlink /etc/systemd/system/multi-user.target.wants/NetworkManager.service.
Removed symlink /etc/systemd/system/dbus-org.freedesktop.nm-dispatcher.service.
Removed symlink /etc/systemd/system/network-online.target.wants/NetworkManager-wait-online.service.
[root@localhost ~]#

8、这样就可以解决问题了.

本篇文章大部分采用了以下博客的信息，现贴链学习
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