Routers work by translating incoming traffic and forwarding it the appropriate computer on your network. When you are accessing webpages and surfing the web, the router sees the traffic going out and knows to forward incoming traffic back to the same computer that requested it. However, if people at home are trying to access a server behind a router, there has to be specific port forwarding to forward their traffic to the particular server. From what you are describing, their Remote Desktop Connection was working until the router was replaced. This suggests that there was port forwarding set up to tell the router to use the Windows 2003 server for Remote Desktop connections. Which ports you would need to forward depends on what protocol/software they are using for their Remote Desktop Connection.

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Steve Kellam
Ruling Elder
Redeemer ARP Church (Blacksburg, VA)
Husband to Holly and father to Bethany, Susannah, and Charlotte (and one on the way!)
“Prayer is as natural an expression of faith as breathing is of life” -- Jonathan Edwards