Strange Android Network Problem

We recently moved some of our APs to a new subnet on our network. Although desktop and laptop computers were unaffected by the change, all Android smart phones refused to work. Although they could connect to the network, they couldn’t access the Internet. After trying many different things, I finally realized it was a DNS problem. Our DHCP was serving up several name servers. The first two were local DNS servers which (to the best of my knowledge) are working fine. However, the Android phones were not resolving host names. Although the DHCP was offering more name server, it appears that Android devices only pay attention to the first two. By moving up an external DNS server to the second spot in my DHCP I was able to fix the problem. However, it would be nice to know why it didn’t work in the first place.