Re: Routing a subnet

Carl Rigney ((no email))
Thu, 19 Oct 1995 18:30:42 -0700

I just wanted to point out that the only time you should need to use
the Netmask table is if you have DIScontiguous subnets (for example,
you've split a class C into different subnets SEPERATED by yet another
network - naughty). Some of the recent recommendations suggesting to
use the Netmask Table don't actually need to.

In particular, if you want to carve up a class C into 16 subnets each
with 14 hosts on it, there's no problem with doing that as long as
they're all contiguous (including the ethernet), just set the netmask
to 255.255.255.240 everywhere.
Another example is to carve up a class C among 7 PortMasters with a
255.255.255.224 netmask so you have one subnet for the ethernet, with
30 hosts on it, and one subnet for the assigned pool on each PM-2E-30.
Of course, you could instead use a 255.255.255.0 netmask and just have
the PortMasters proxy arp on behalf of their assigned pools, which would
be much simpler. But if you wanted to have 3 PortMasters at one site
and 3 at another, subnetting can be useful.

--
Carl Rigney
cdr@livingston.com