The proper way to configure interfaces on Ubuntu

Apr 8, 2015

Discovered that in recent Ubuntu versions, the following is the “official” way to up and down interfaces cleanly.

1. Edit /etc/network/interfaces adding your entry similar to below:

   # The loopback network interface
   auto lo
   iface lo inet loopback
   
   # The primary network interface
   auto eth0
   iface eth0 inet static
           address 10.1.24.30
           netmask 255.255.254.0
           network 10.1.24.0
           broadcast 10.1.25.255
           gateway 10.1.24.1
           # dns-* options are implemented by the resolvconf package, if installed
           dns-nameservers 10.11.11.11
           dns-search herpderp.com
   
   auto eth3
   iface eth3 inet static
           address 192.168.24.29
           netmask 255.255.254.0
           mtu 9000
   

2. ifup eth3 to bring up eth3 with its new configuration.

3. Want to fully clean an interface:

   ifdown eth3
   # For the following, sometimes flushing helps ;P
   # http://unix.stackexchange.com/questions/100588/using-ip-addr-instead-of-ifconfig-reports-rtnetlink-answers-file-exists-on-de
   ip addr flush dev eth3