Today we lost one of our DHCP servers (a 2003 box - maybe a sign). It only had one scope on it but we didn't have a backup for it.

We promptly setup a new 2012 R2 server with the same scope and we started seeing activity almost right away. One thing we're trying to deal with now is that the new DHCP server is giving out ip numbers that are already assigned to clients from the old DHCP server and those numbers are showing up in DHCP as BAD_ADDRESS.

What is the best way to deal with this on the clients? Reboots? I'd rather not have to ipconfig / release and renew on every

Hi

 First i recommned you to check this new 2012 dhcp already authorized to domain.Also please check the old server already on domian with auhorized dhcp server list,

Run this to check "netsh dhcp Show server" if the old dhcp still on list just delete this from domain,run "netsh dhcp delete server olddhcp.yourdomain.local xxx.xxx.x.x(ip address)"

Then finaly authorized again this new 2012 and check,