On Tue, 2006-04-04 at 21:02, Mike McCarty wrote: > > > > ARP is *only* used to determine MAC addresses. MAC addresses are *only* > > used within a subnet. > > Thank you. I thought I was beginning to lose my mind, > or had completely missed the boat on TCP/IP. TCP works over all kinds of media. Some kinds are point-to-point like serial links where whatever you put into one end comes out in only one place at the other. Ethernet is a broadcast media where all stations on the subnet could see what any of them send, but they don't want to. The MAC address lets everything that doesn't want your packet ignore it efficiently, and to put the MAC address in the packet the sender must first find the one corresponding to the TCP address via ARP. -- Les Mikesell lesmikesell@xxxxxxxxx