[comp.protocols.tcp-ip] Subnets connected by a gateway not part of the subnetted network

jas@MONK.PROTEON.COM (John A. Shriver) (12/23/87)

You can't do that.  A network must be contiguous.  This is stated on
RFC1009 page 5: "The distinction between subnets of such a subnetted
network must not be visible outside that network".

Since that gateway is not part of the partitioned subnetted network,
how in the dickens would it know which half of the network to send a
given packet to?  It would not have the subnet routing table.
Gateways outside a subnetted network send a packet to the nearest
point on that network.  Then subnet routing carries the packet to the
right subnet.  While this may take more hops than is optimal, the
benefits of abstraction make it worthwhile.

Exactly the same restriction applies to DECnet.  A DECnet area must be
contiguous.  It also has the same extra-hop phenomenon in inter-area
routing.