[CentOS] Subnet expansion

Tue Jul 26 11:53:02 UTC 2011
John Hodrien <J.H.Hodrien at leeds.ac.uk>

On Tue, 26 Jul 2011, Fajar Priyanto wrote:

> Hi all,
> Can pls share your experience on this?
>
> Currently I have this network:
> 10.1.16.0/22.
> 10.1.16.0-10.16.17.254 are DHCP managed
> 10.1.18.0-10.1.19.254 are statically assigned
>
> If I need to expand it to:
> 10.1.16.0/20
>
> 1. What is the best way to do it with minimal network disruption?

> 2. If I keep some machine with 22 subnet mask, will it still be able
> to talk to the other machines in it's range?

Seeing as noone else has posted anything, you can have my thoughts.

I think the answer to this part is not trivially.  A machine in the /20 subnet
will expect to be able to talk directly to a machine within the /22, but that
machine will want to talk via a router.  You can hide subnets within subnets
using arp-proxying, but I'm not sure there's an easier way.

A machine within the /22 would be able to talk to any other machine within
that /22 (even if they're configured to use /20), but won't be able to happily
talk to machines within the /20 but outside of the /22.

jh