This is easy to find anywhere, and it’s here too. This one includes the dns-* lines that will be read by resolvconf(8).
root@server:/etc/network# cat interfaces # This file describes the network interfaces available on your system # and how to activate them. For more information, see interfaces(5). # The loopback network interface auto lo iface lo inet loopback # The primary network interface auto eth0 iface eth0 inet static address 192.168.1.251 netmask 255.255.255.0 network 192.168.1.0 broadcast 192.168.1.255 gateway 192.168.1.254 dns-nameservers 192.168.1.250 dns-search mydomain.local
Also, here’s a cheatsheet for setting that netmask:
255.255.255.252 /30 2 nodes 255.255.255.248 /29 6 nodes 255.255.255.240 /28 14 nodes 255.255.255.224 /27 30 nodes 255.255.255.192 /26 62 nodes 255.255.255.128 /25 126 nodes 255.255.255.0 /24 "Class C" 254 nodes
Note that the number of nodes is the total number of addresses, less two. It’s less two because the lowest value is the address of the entire network. The highest value is the broadcast address. So if the netmask is 0, then the lowest value is 0, and that’s the address of the network, and the highest value is 255, which is the broadcast address.