Question : Windows Network Computers Cannot Communicate Internally

I have a client running Windows SBS 2003.  There is a D-Link DI-604 Router and a Switch.  There are 8 PCs running WinXP SP2 on the network. (Each named WK01, WK02, etc.).  The router is distributing the IP Addresses.

These are all new equipment that was setup 3 weeks ago.  Everything worked fine up to yesterday.

The computers are able to access the Internet and their email (which is hosted off-site).  However, none of the computers are able to access the server, even though previously they have.  The client/server accounting software no longer works.  And the for network shares (M:, N:, O:, S:) can no longer be accessed.  I had disconnected the shares and rebooted a workstation but they are no longer mapping the drives.

The workstations cannot ping the server IP Address. The server cannot ping any of the workstations either, except for WK04, and it does so intermittently.  The workstations cannot ping each other, but usually they can ping WK04 and get a response.

Since the router and switches seemed hot, I unstacked them, thinking perhaps the router was overheating and causing issues.  They have cooled down and I'm still having the same problem.
I have replaced the ethernet cable going from the server to the switch. Same problem.
I have removed the switch and plugged the server directly into the router. Same problem.
I am currently waiting on the replacement router so I can see whether that is the issue.

As far as I can tell, the router firewall is not configured to block anything.
I have checked the DHCP settings on the server and they are turned off.
I have verified that there are no group policies that have been started.

Answer : Windows Network Computers Cannot Communicate Internally

Your client's shouldn't have your ISP's IP address for DNS server. They should point to your SBS server for DNS.

I would disable DHCP service on your router and enable it on your SBS server. Once enabled configure it to give out correct DNS server and other settings (e.g. gateway). Again -- DNS that clients should use is DNS on your SBS server (your Active Directory server).

Also DNS settings on your SBS server (under TCP/IP settings) should point ti itself. You can simply configure 127.0.0.1 as Preferred DNS on your SBS server under TCP/IP settings. Leave Alternative DNS Settings blank.

Then open DNS MMC on SBS and right click name of your server. Click Forwarders tab and enter IP address of your ISP DNS Servers. This will allow you fast name resolution of internet resources.

Let us know if you need more help on any of these steps.

Once you change this and restart the clients -- the problems should go away.

Miha