HEDRICK@RED.RUTGERS.EDU (Charles Hedrick) (06/11/86)
We have an equivalent of your Vitalink network, using Applitek bridges. We make sure that one gateways off that network does "promiscuous ARP". This is a generalization of the "ARP hack" that has long been used for subnetting. It generalizes it by having the gateways accept an ARP for absolutely any address at all. If they are the appropriate gateway, they respond with their Ethernet address. If not, they respond with the Ethernet address of the correct gateway. (If you have several gateways that do this, you can modify the code so that a gateway does not respond for another gateway if the second is known to be capable of responding for itself.) This is the ARP equivalent of an ICMP redirect. Note that you only need one such gateway on a network, since it can hand out the Ethernet addresses of the other gateways. This is the only technique we can think of that can handle complex networks built with systems like the Vitalink and Applitek. (I do not approve of such bridges, but I can't prevent people from buying them, so I've had to come up with a way to live with them.) -------