OD Replica not working

We are running OD replica on an Xserve 10.4.10, of course when the network works all is great, but when the network is down we are dead in the water!!! Teachers are unable to login to their computers. I thought that the replica held all the info needed to let users login and work as usual. I am thinking that it is something with the DNS settings? When we were down, I looked at the crash log and received the "DNS cannot be resolved error" But if any of you can steer me in a direction to start to resolve this problem I would greatly appreciate any help. I am not the person who set up the ODM or any of the replicas, but I am the one that receives all of the back lash when things don't work!!