Proxy Arp/Subnets

That's what I thought you were saying, but I wanted to make sure. How does that affect the flow of data? I guess it would depend on the infrastructure between the to nodes.

If Host A and Host B are directly connected, communication would only work in one direction?

Host A would be able to send to Host B with no problem. However if Host B wanted to send to Host A then Host B would compare the address of Host A with the subnet mask held on Node B and conclude that Host A was on a different network. It would therefore send the packet to its default gateway (whatever that was) rather than sending it direct to Host A. The packet would therefore probably go astray. I say probably because there might be scenarios that would still cause the communication to "work" (such as ARP poisoning or Host B's default gateway device reditrecting the packet to Host A after all). Strange things have been known to happen from time to time

If that is a one-way communication stream, what happens to return traffic? That would get sent to the default gateway as well, correct? If Host A were to ping Host B the echo packet would make it to Host B, but the return echo reply would not? (If I have the ICMP terms correct).

I guess what I am really getting at is, would this be a logic setup of IP/Subnet masks for two hosts that you would want to communicate?

I'm almost certain that return traffic would be subject to the same rules. So A Ping from Host A would arrive correctly at Host B but then Host B would misdirect the reply packet to its default gateway so the reply would never make it back to Host A. So, even though the Ping actually arrived and Host B did reply, as far as Host A is concerned the "ping" would fail.
My only unease with this is around ARP - Presumably Host B would have a MAC address for Host A (having heard from it), so perhaps it would use it (this being a lower level function of the OSI model) in preference to making a higher level IP address based routing decision. What does everyone else think on this point?

I'm not sure either. Would the default gateway know how to find Host A?

For all of this to work we would need to have host A and host B on the same physical network ( vlan ) and have a default gateway and routing set up with no auto summary.

If that were the case then It seems like it would work. Having the ping routed to the destination, but the return on the same lan...???

I'm not sure at all... I'm more curious about this.. ?? Anyone else???