Shaul Karl wrote on 2003-07-08:
> I still don't get something. Quoting section 7 of the IP Sub-Networking
> Mini-Howto:
>
> For the sake of this example, let us assume that you have decided to
> subnetwork you C class IP network number 192.168.1.0 into 4 subnets
> (each of 62 usable interface/host IP numbers). However, two of these
> subnets are being combined into a larger single network, giving three
> physical networks.
> These are :-
>
> ______________________________________________________________________
> Network Broadcast Netmask Hosts
> 192.168.1.0 192.168.1.63 255.255.255.192 62
> 192.168.1.64 192.168.1.127 255.255.255.192 62
> 192.168.1.128 192.168.1.255 255.255.255.128 124 (see note)
> ______________________________________________________________________
>
> Note: the reason the last network has only 124 usable network
> addresses (not 126 as would be expected from the network mask) is that
> it is really a 'super net' of two subnetworks. Hosts on the other two
> networks will interpret 192.168.1.192 as the network address of the
> 'non-existent' subnetwork. Similarly, they will interpret
> 192.168.1.191 as the broadcast address of the 'non-existent'
> subnetwork.
>
> So, if you use 192.168.1.191 or 192 as host addresses on the third
> network, then machines on the two smaller networks will not be able to
> communicate with them.
>
> \begin{interruptRequest}
>
> How does the 2 smaller networks know that 192.168.1.191 and 192 were
> initially a broadcast and network addresses? Would they treat any one of
> 192.168.*.19[12] in the same way?
>
> \end{interruptRequest}
>
As far as I understand, they assume that sub-networking is uniform:
they know the full network mask and know it is subnetted with a given
subnet mask. They assume it doesn't only apply to their own subnet
but to each subnet of the network. No, they wouldn't treat
192.168.*.* in this way, the full network mask seems to be
255.255.255.0 so they only assume things about "sibling subnets" i.e.
192.168.1.*.
--
Beni Cherniavsky <[EMAIL PROTECTED]>
If I don't hack on it, who will? And if I don't GPL it, what am I?
And if it itches, why not now? [With apologies to Hilel ;]
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