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         UG    0      0        0 eth0   U     0      0        0 eth0 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".


According to nixCraft:

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

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

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    The source of the "generality" thing seems to be the TLDP: tldp.org/LDP/nag/node75.html It's just odd that the output of route seems to be the only place the actual term "genmask" is used. Everywhere else it's "netmask." E.g. in my system's man files, "netmask" shows up 207 times, but "genmask" is only mentioned in the route man page. – dirtside Jun 9 '15 at 0:46
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    One thing I like about the various unixen is that the primary tools do not typically/deliberately obscure ideas. It is sad to see this use of 'genmask' when 'netmask' would fit just as well in that output. – sage Jul 27 '17 at 21:08

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