subnetting C class into /26 /25 /26, why can this be done?

[Olivier Nicole]

Christoffer Pio wrote:
> Is it not possible to subnet a C class into 3 nets, like
> 
> 0-63
> 64-191  <-- Offending network (?)
> 192-255
>
> If so, why is this?

I think you got explanations on the why.

Now it should still be possible to subnet the way you want I think.

While I would never recommend it, think routing should go with the
most significant mask for a given address.

So if you subnet:

1) x.x.x.0/26
2) x.x.x.192/26
3) x.x.x.0/24

you should be able to do the trick.

An address in the range 0-63 will match both mask 1) and 3) but mask
1) is most significant (more bits, higer value) so the packet will be
routed to subnet 1).

Same thing for a packet in the range 192-255, with subnet 2) and 3),
it will be router to subnet 2).

And a packet in the range 64-191 will only match the subnet 3) so it
will go to the subnet 3).

IF I AM NOT WRONG, this should work, but it is definitely nasty.

If you absolutely need 2 subnets of 64 addresses and one of 128,
doing:

1) x.x.x.0/26
2) x.x.x.64/26
3) x.x.x.128/25

is nicer and will result in the ranges 0-64, 64-127 and 128-255.

Olivier