Internet connection and Firewall problem

[yennhile]

Hi Will and all gurus,
I hope your expertise will help me solve the problem at my client's company. Our network: Cable Router --> Firewal (IPCOP an open-source firewall) --> switches ---> server and PCs. The server is a File/Exchange/Backup Server. We lost Internet connection for over 2 days now, after turning on the filter services on Ipcop. What else I had added: MS SharePoint service, MS Exchange server SP2. What then happened was the email attachments were chopped and users did not receving emails from outside. Email was going out, but not coming in. (This was fixed yesterday.) I turned off all services and reset the router and firewall. I was able to ping all interfaces: router, firewall from the server side, but still there is no internet connection from LAN. I checked DHCP on the server. server could not recognize teh DHCP on the firewall, although it had firewall as the authorized server. Would that be probably b/c it was the Linux box?
I started out from scratches, tried to go without the firewall, moved DHCP to the Windows server. But we can not get rid of it, simply b/c the firewall has static IPs. The server is a one-NIC server. At the cable modem/router, I can get online. At the server side, I can ping any interface, including web site. But I can not get a web page to display. I reconfiged the server's adapter with the DNS servers from the ISP or the Host company, but it did not help. I tried to repair the interface (remotely from home),
C:\>netsh interface ip delete arpcache
Ok.

But still, no Internet connection!

I need your help and any IT expert help if available with this big issue.
Your inputs and help are appreciated.
I hope I made good presentation of the problem.


Yen-Nhi Le

[Will.Spencer]

This sounds like a doozie of a problem.

If you can get online from the cable router, then you know the network trouble must be either on the firewall or on your switches, server, and PC's.

Obviously, as this error occurred right after you enabled filters on the firewall, the firewall is already the prime suspect.

If you can ping any interface from the server, then I have to assume that everything is getting DHCP addresses from somewhere.

Most likely, there is a configuration error in IPCop.

If you turn off IPCop and just implement "normal" routing on the firewall box, does the network start working again?