From: Eric Smith
which would respond to ARP requests for non-local
addresses and reply
with the router's MAC address (on that interface), specifically in
order to make classful-only hosts work on a CIDR network.
Yeah, Proxy ARP (an early RFC here:
https://www.rfc-editor.org/rfc/rfc1027.txt
but IIRC it was people at CMU who first came up with the idea; this RFC is
from people at UT-Austin, documenting it) was
originally done to support
subnetting (see
https://www.rfc-editor.org/rfc/rfc917.txt
for more) when it was first introduced - for hosts for which people didn't
have the source, but needed to attach it to a subnetted network.
Subnetting was a stage before CIDR (which took subnetting and Carl-Herbert
Rokitansky's 'supernetting' and mushed them together).
Noel