netmask

networking A 32-bit bit mask which shows how an Internetaddress is to be divided into network, subnet and host

parts. The netmask has ones in the bit positions in the 32-bit address

which are to be used for the network and subnet

parts, and zeros for the host part. The mask should contain

at least the standard network portion (as determined by the

address's class), and the subnet field should be contiguous

with the network portion.

If a `+' (plus sign) is given for the netmask value, then the

network number is looked up in the NIS netmasks.byaddr map

(or in the /etc/netmasks) file if not running the NIS service.

Unix manual page: ifconfig(8).

(1995-01-30)