Difference between “genmask” and “netmask”

linux-networkingnetworkingrouting

In the output of route -n on Linux, you get something like this:

Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         10.0.0.1        0.0.0.0         UG    0      0        0 eth0
10.0.0.0        0.0.0.0         255.255.255.0   U     0      0        0 eth0
169.254.169.254 0.0.0.0         255.255.255.255 UH    0      0        0 eth0

I know that Genmask refers to the netmask portion of the route, but why is it called "Genmask" instead of "netmask" like it is everywhere else? This is literally the only place I've ever seen "Genmask".

Best Answer

According to nixCraft:

Genmask : The netmask for the destination net; 255.255.255.255 for a host destination and 0.0.0.0 for the default route.

It's called 'genmask' because it shows the 'generality' (i.e. the netmask) of the route.

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