Re: Class C subnetting

Glynn Clements (glynn@sensei.co.uk)
Tue, 5 Aug 1997 00:50:27 +0100


Dave Wreski wrote:

> Hi all. I'm building a firewall with three interfaces, and I'd like to
> subnet the Class C that my ISP has given me. I'd like to split it into
> four networks, each of which would have 62 hosts. I'm receiving 'network
> is unreachable' problems when trying to add a route to the second network.
>
> I'm using a crossover cable to route between two boxes on eth0 of each.
>
> I was given 38.162.122.0. So, this is what I did on the machine that will
> be on network 0.
>
> ifconfig eth0 38.162.122.10 netmask 255.255.255.192 broadcast 38.162.122.63
> route add -net 38.162.122.0 dev eth0

38.162.122.0 isn't a class C network; it's a (256-address) subnet of a
class A network.

Try using:

route add -net 38.162.122.0 netmask 255.255.255.192 dev eth0

This may or may not help.

> This seems to work ok, but I don't know how to add a route to the other
> box, which is connected via a single crossover cable. In other words,
> there's no router involved.

Try something like:

ifconfig eth0 38.162.122.65 pointopoint 38.162.122.193
route add -host 38.162.122.193

-- 
Glynn Clements <glynn@sensei.co.uk>