We operate in a W2K3 AD domain. The domain has two DCs replicating one another. The Primary DC is W2K3 R2 SP-2, and the alternate DC is W2K3, SP-2. If I enable the firewall on either of these DCs, FRS will not replicating (Event ID:13508), and clients cannot resolve DNS or possibly RPC connection problems. I can say that if the firewalls are disabled these problems go away. I followed the steps as per article KB555381 (How to configure Windows Server 2003 SP1 Firewall for a Domain Controller) on both DCs and the communications problems still exist. I modified the registry and opened all the suggested ports, enabled the firewalls and rebooted both DCs. After the reboot and the firewalls enabled the same problems exist. At this point I disabled the firewalls until we can figure out how to correct the problem. Any feedback would be appreciated.