dhcp的, ip addr是这样子的
root@debian:~# ip addr
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: ens18: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq state UP group default qlen 1000
link/ether aa:aa:00:09:a3:67 brd ff:ff:ff:ff:ff:ff
inet xxx.xxx.xxx.105/20 brd 104.225.159.255 scope global ens18
valid_lft forever preferred_lft forever
inet6 fe80::xxxx:ff:xxxx:xxxx/64 scope link
valid_lft forever preferred_lft forever
3: ens19: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN group default qlen 1000
link/ether ba:aa:00:09:a3:67 brd ff:ff:ff:ff:ff:ff |