On most installations, which program identifies when a network connection goes down and identifies when a new DHCP request needs to occur. I have an embedded system that I would like this to work on. Unfortunately, I do not know which tool to add that will give me the desired result.

Thanks
Doug Bailey

If it's an embedded system it's probably using the DHCP client udhcpc from busybox. Its detailed behaviour is specified in a script, usually /usr/share/udhcpc/default.script

If the network goes down, I'm not sure the udhcpc process even finds out until it tries to renew the lease, which might be hours later. Can you just set a cron job or a simple loop to check for network connectivity and restart networking if it is out?

There is a discussion of udhcpc in the embedded context here:

http://www.nslu2-linux.org/wiki/HowTo/GetDHCPWorking

One of the suggestions is to configure udhcpc to fall back to a usable static address, so that you can still communicate with the device if dhcp fails.