> I'm sure that this is blindingly obvious, but I have not been able to find any
> references to it...
>
> I have a class C address for my network - As part of my firewall I will have a
> dual homed sparc 5 running Solaris 2.5. I want to forward packets from one
> interface to the other - am I allowed to use netmask 255.255.255.0 with both
> interfaces in the same subnet e.g.
>
> 192.100.100.1 and the other on 192.100.100.2
>
> I have tried to set routing up for this up and failed so the question is
>
> Do I have to subnet a class C address to achieve packet forwarding or is there
> some trick in the routing that I am missing??
>
> All the references on this soft of setup assume that you are doing packet
> forwarding from something like 192.100.100.1 to 192.100.99.1, but I only have a
> class C from my ISP and cannot affort to loose the half my IP addresses that
> subnetting would cause.
>
> Paul.
> --
>
Yes you do have to use subnetting to implement routing on a single
class "c" address.
To route between two networks, the two networks have to have a
different network number (or else, how would it know when to route?).
To get different network numbers on a class "c" you have to use
subnetting.
e.g.
use subnet 255.255.255.192
this will give you four networks of 64 hosts:
x.x.x.0-63, x.x.x.64-127, x.x.x.128-191, x.x.x.192-255
Set one interface to: 192.100.100.65
Set the other to: 192.100.100.129
(don't use the first or last address in each subnet as these are the
network and broadcast addresses for that subnet).
I always believed that you couldn't use the first or last subnet
(i.e. 0-63 and 192-255) - but recently I heard that this was OK so
long as your routers were new enough(!) and you follow the rule above
(i.e. don't use first or last address in the subnet). I'd be
interested in any opinions on this....
Regards (and good luck Paul),
Ben
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