Josh, Bear in mind that there's the MAC address, 6 bytes long, usually represented in hex as: xx-xx-xx-xx-xx-xx and this needs to be unique. Manufacturers assign these from blocks that they are granted (sold!) by the relevant authorities. IP addresses (currently 4 bytes, usually represented in "decimal dot" notation: xxx.xxx.xxx.xxx) are assigned at run time, either statically by the firmware of the device, aided and abetted by a user, or dynamically by DHCP... On Mon, 26 Jun 2006 16:19:29 -0400, Josh Koffman wrote: >... > My problem with DHCP is that if I randomly hand out IP addresses, how > can I ensure that the device at 192.168.1.32 is going to be the same > each time? You can't! It's a bad fit for a device that will be addressed solely by its IP address, rather than a URL. > The devices I'm thinking about will always need to be > repeatably addressed based on their physical location, which is > something that Ethernet doesn't really care about - you can plug your > cable in anywhere and still get a connection. Perhaps a combo of > assigning an IP address via DHCP then using the MAC address as an > identifier? Various manufacturers of embedded devices use different strategies - most of the Routers, WAPs, Network Storage units start out with a fixed address and you then have to change it as part of the installation process - a pain since the address they have chosen may not be on your subnet and you have to reconfigure the PC to access it and change it to something more useful. Or worse, they may have chosen an address you're already using! Some manufacturers have a piece of PC software that looks for their devices by sending out some sort of broadcast saying "anyone there?" - the device(s) respond and you can then set their IPs. However I came across a method I'd not seen before, yesterday. It's an Axis video server, and its MAC address is also its serial number, on a label with a bar-code underneath. Having powered-up the device and connected to the network, you start up a command-line session on a PC and then enter: ARP -s PING -l 408 -t This sets up a table entry so that the device is found from that PC as if it was on the IP address you've entered, and you can then PING it. I presume the PING allows the device to detect the IP address it's being given, and perhaps the 408-byte length is a trigger for it to assume that address - anyway, that's what happens! Thereafter you can start a browser and set up all the other parameters, using the IP address to access it - clever! :-) Cheers, Howard Winter St.Albans, England -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist