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常常都被虚拟机的网络折腾得颠三倒四，做点笔记吧。
问题：选择 NAT 后并配置好 IP 和 NetMask 之后，可以 ping 通主机，但连不通 Internet。
解决：手动配置默认网关。
步骤：
在虚拟网络编辑器里，找到网关配置，这里是 192.168.171.2。
在虚拟机设置里，确认选择 NAT。
IP 和 NetMask 已经配置：
[root@localhost ~]# ifconfig ens33
ens33: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 192.168.171.128 netmask 255.255.255.0 broadcast 192.168.171.255
inet6 fe80::20c:29ff:feba:ba7c prefixlen 64 scopeid 0x20<link>
ether 00:0c:29:ba:ba:7c txqueuelen 1000 (Ethernet)
RX packets 281023 bytes 361357640 (344.6 MiB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 68897 bytes 14016800 (13.3 MiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
可以 Ping 通主机，但无法连接 Internet：
[root@localhost ~]# ping 192.168.171.1
PING 192.168.171.1 (192.168.171.1) 56(84) bytes of data.
64 bytes from 192.168.171.1: icmp_seq=1 ttl=128 time=0.416 ms
64 bytes from 192.168.171.1: icmp_seq=2 ttl=128 time=0.318 ms
64 bytes from 192.168.171.1: icmp_seq=3 ttl=128 time=0.348 ms
64 bytes from 192.168.171.1: icmp_seq=4 ttl=128 time=0.262 ms
^C
— 192.168.171.1 ping statistics —
4 packets transmitted, 4 received, 0% packet loss, time 3001ms
rtt min/avg/max/mdev = 0.262/0.336/0.416/0.055 ms
[root@localhost ~]# ping 8.8.8.8
connect: Network is unreachable
检查路由表：
[root@localhost ~]# netstat -nr
Kernel IP routing table
Destination Gateway Genmask Flags MSS Window irtt Iface
192.168.122.0 0.0.0.0 255.255.255.0 U 0 0 0 virbr0
192.168.171.0 0.0.0.0 255.255.255.0 U 0 0 0 ens33
手动添加网关：
[root@localhost ~]# route add default gw 192.168.171.2
[root@localhost ~]# netstat -nr
Kernel IP routing table
Destination Gateway Genmask Flags MSS Window irtt Iface
0.0.0.0 192.168.171.2 0.0.0.0 UG 0 0 0 ens33
192.168.122.0 0.0.0.0 255.255.255.0 U 0 0 0 virbr0
192.168.171.0 0.0.0.0 255.255.255.0 U 0 0 0 ens33
再次尝试：
[root@localhost ~]# ping 8.8.8.8
PING 8.8.8.8 (8.8.8.8) 56(84) bytes of data.
64 bytes from 8.8.8.8: icmp_seq=1 ttl=128 time=23.4 ms
64 bytes from 8.8.8.8: icmp_seq=2 ttl=128 time=26.5 ms
64 bytes from 8.8.8.8: icmp_seq=3 ttl=128 time=22.5 ms
64 bytes from 8.8.8.8: icmp_seq=4 ttl=128 time=29.2 ms
^C
— 8.8.8.8 ping statistics —
4 packets transmitted, 4 received, 0% packet loss, time 3007ms
rtt min/avg/max/mdev = 22.524/25.448/29.255/2.666 ms
删除刚刚添加的网关，重现之前的错误：
[root@localhost ~]# route del default gw 192.168.171.2
[root@localhost ~]# netstat -nr
Kernel IP routing table
Destination Gateway Genmask Flags MSS Window irtt Iface
192.168.122.0 0.0.0.0 255.255.255.0 U 0 0 0 virbr0
192.168.171.0 0.0.0.0 255.255.255.0 U 0 0 0 ens33
[root@localhost ~]# ping 8.8.8.8
connect: Network is unreachable
参考链接：
https://www.freebsd.org/doc/h… https://unix.stackexchange.co…
