[CentOS] Simple routing question

[Cliff Pratt]

On Wed, Sep 5, 2012 at 9:00 AM, James B. Byrne <byrnejb at harte-lyne.ca> wrote:
>
> On Tue, September 4, 2012 16:51, Les Mikesell wrote:
>>
>> That should happen directly without C's involvement if the netmask is
>> 255.255.0.0 on A and B's eth1 interfaces.
>
> It is not.  The netmask on those interfaces is 255.255.255.0.
>
>>
>>> Instead it goes to Eth0 on C where it dies as one would
>>> expect.
>>
>> Why does C have both internet and LAN addresses on the same
>> interfaces?
>>
>
> I am experimenting to see if this arrangement is workable.  I want to
> know if it is possible to have two separate 192.168.x subnets on the
> same network.  Why?  I do not have a purpose in mind.  I am just
> checking out whether it can work or not.
>
> If it is impossible then then I will discover why that is so, which I
> think will be useful in itself.
>
IMO you need to configure the two subnets separately and set the
netmask to 255.255.255.0. Then route traffic between the LANs via
either the firewall or another routing device on the shared network.

I've done similar in the past to migrate from one IP range to another.

Having both networks connect to the firewall router is risky in case
of a misconfiguration.

Cheers,

Cliff