我的系统是刚刚安装的Ubuntu 18.04。我格式化了“/”部分，但保留了“/home”部分。
重装之前电脑是Ubuntu14.04，重装的时候网络就不对了，现在还是报错。
当我 ping 一个域时，它运行得很好，但是 wget apt 和浏览器无法工作。
加装USB无线网卡后，网络没问题，如何排查问题？
$ ping -c3 askubuntu.com
PING askubuntu.com (151.101.65.69) 56(84) bytes of data.
64 bytes from 151.101.65.69 (151.101.65.69): icmp_seq=1 ttl=52 time=134 ms
64 bytes from 151.101.65.69 (151.101.65.69): icmp_seq=2 ttl=52 time=133 ms
64 bytes from 151.101.65.69 (151.101.65.69): icmp_seq=3 ttl=52 time=132 ms
--- askubuntu.com ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2002ms
rtt min/avg/max/mdev = 132.458/133.681/134.628/1.000 ms
$ wget askubuntu.com
--2019-01-29 12:05:12-- http://askubuntu.com/
Resolving askubuntu.com (askubuntu.com)... 151.101.65.69, 151.101.1.69, 151.101.193.69, ...
Connecting to askubuntu.com (askubuntu.com)|151.101.65.69|:80... failed: Connection refused.
Connecting to askubuntu.com (askubuntu.com)|151.101.1.69|:80... failed: Connection refused.
Connecting to askubuntu.com (askubuntu.com)|151.101.193.69|:80... failed: Connection refused.
Connecting to askubuntu.com (askubuntu.com)|151.101.129.69|:80... failed: Connection refused.
以下是其他信息。
$ 路线-n
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
0.0.0.0 192.168.0.1 0.0.0.0 UG 20100 0 0 enp2s0
169.254.0.0 0.0.0.0 255.255.0.0 U 1000 0 0 enp2s0
192.168.0.0 0.0.0.0 255.255.255.0 U 100 0 0 enp2s0
$ ifconfig -a
enp2s0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 192.168.0.199 netmask 255.255.255.0 broadcast 192.168.0.255
inet6 fe80::9997:3ae3:6798:1ac8 prefixlen 64 scopeid 0x20<link>
ether 00:ea:01:28:99:88 txqueuelen 1000 (Ethernet)
RX packets 141444 bytes 136582388 (136.5 MB)
RX errors 0 dropped 79 overruns 0 frame 0
TX packets 82546 bytes 5792934 (5.7 MB)
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 6524 bytes 984671 (984.6 KB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 6524 bytes 984671 (984.6 KB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0