Ubuntu でNICを追加したときの設定についてメモ。

NIC を追加して起動。
設定一覧を表示してみます。

root@ubuntu:~# ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default
    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: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
    link/ether 08:00:27:76:1a:04 brd ff:ff:ff:ff:ff:ff
    inet 192.168.1.6/24 brd 192.168.1.255 scope global eth0
       valid_lft forever preferred_lft forever
    inet6 2408:211:a84:2b00:a00:27ff:fe76:1a04/64 scope global mngtmpaddr dynamic
       valid_lft 14109sec preferred_lft 12309sec
    inet6 fe80::a00:27ff:fe76:1a04/64 scope link
       valid_lft forever preferred_lft forever
3: eth1: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN group default qlen 1000
    link/ether 08:00:27:6f:2a:e5 brd ff:ff:ff:ff:ff:ff
4: docker0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state DOWN group default
    link/ether 56:84:7a:fe:97:99 brd ff:ff:ff:ff:ff:ff
    inet 172.17.42.1/16 scope global docker0
       valid_lft forever preferred_lft forever


eth1 の NICが IPアドレスが振られていません。
これを設定します。
設定ファイルは /etc/network/interfaces にあります

root@ubuntu:~# vi /etc/network/interfaces


  auto eth1
  iface eth1 inet dhcp

NIC を起動します。

root@ubuntu:~# ifup eth1
Internet Systems Consortium DHCP Client 4.2.4
Copyright 2004-2012 Internet Systems Consortium.
All rights reserved.
For info, please visit https://www.isc.org/software/dhcp/

Listening on LPF/eth1/08:00:27:6f:2a:e5
Sending on   LPF/eth1/08:00:27:6f:2a:e5
Sending on   Socket/fallback
DHCPDISCOVER on eth1 to 255.255.255.255 port 67 interval 3 (xid=0x6a8cc74e)
DHCPREQUEST of 192.168.56.101 on eth1 to 255.255.255.255 port 67 (xid=0x6a8cc74e)
DHCPOFFER of 192.168.56.101 from 192.168.56.100
DHCPACK of 192.168.56.101 from 192.168.56.100
bound to 192.168.56.101 -- renewal in 549 seconds.

※確認
root@ubuntu:~# ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default
    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: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
    link/ether 08:00:27:76:1a:04 brd ff:ff:ff:ff:ff:ff
    inet 192.168.1.6/24 brd 192.168.1.255 scope global eth0
       valid_lft forever preferred_lft forever
    inet6 2408:211:a84:2b00:a00:27ff:fe76:1a04/64 scope global mngtmpaddr dynamic
       valid_lft 13676sec preferred_lft 11876sec
    inet6 fe80::a00:27ff:fe76:1a04/64 scope link
       valid_lft forever preferred_lft forever
3: eth1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
    link/ether 08:00:27:6f:2a:e5 brd ff:ff:ff:ff:ff:ff
    inet 192.168.56.101/24 brd 192.168.56.255 scope global eth1
       valid_lft forever preferred_lft forever
    inet6 fe80::a00:27ff:fe6f:2ae5/64 scope link
       valid_lft forever preferred_lft forever
4: docker0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state DOWN group default
    link/ether 56:84:7a:fe:97:99 brd ff:ff:ff:ff:ff:ff
    inet 172.17.42.1/16 scope global docker0
       valid_lft forever preferred_lft forever

eth1 に IPアドレスが割当たりました。