I'm trying to understand the syntax of ifupdown a bit better, and on several sites detailing fairly straightforward static configurations, the example documentation includes a line stating `network 192.168.0.0' -- or something obviously similar. For example, # The loopback network interfaceauto lo eth0iface lo inet loopback# The primary network interfaceiface eth0 inet static    address 192.168.10.33    netmask 255.255.255.0    broadcast 192.168.10.255    network 192.168.10.0    gateway 192.168.10.254 dns-nameservers 192.168.10.254What exactly does this line do? I can't imagine that it contains anything that the netmask + address doesn't convey about, for example, broadcast addresses. There is much useful documentation about the myriad array of powerful things that one can do with /etc/network/interfaces available online. Almost all of it details various aspects of networking. Therefore, googling isn't terribly helpful! 
In Debian-derived flavours, what does the 'network' line in /etc/network/interfaces actually do?
networking;ifconfig
The network doesn't have to be specified as it is simply the result of address & netmask (& is a binary and):192.168.10.33 & 255.255.255.0 = 192.168.10.0It may make it easier to understand by showing it in binary:  11000000.10101000.00001010.00100001 (192.168.10.33)& 11111111.11111111.11111111.00000000 (255.255.255.0)-------------------------------------  11000000.10101000.00001010.00000000 (192.168.10.0)