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I configure a number of forwarder ports on my home router for RDC

3389 -> Windows Vista desktop : 3389

3390 -> Windows Vista laptop : 3389

3391 -> Windows 2008 server : 3389

3392 -> Windows 2008 server : 3389

All was working fine until I swapped my laptop for another with Dell. After setting up the new laptop, I enabled Remote Desktop as usual, firewall disabled, but cannot connect to it from the outside Internet. I tried rebooting my router, changing the router port to 3388, to no avail. The other computers still connect fine. Nothing to do with Network level authentication either.

I can only RDC to the laptop from the LAN. Any ideas what may be the problem?

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Forwarding on router is configured for specific IP within network, perhaps new laptop got new IP? – superego Sep 9 '09 at 13:10
They are all static IP addresses. – icelava Sep 9 '09 at 13:16
how did you do the port-forwarding in the router? Some routers do port-forward to IP addresses, some do portforwarding to hostnames – caliban Sep 9 '09 at 13:34
it is by IP addr. i use the same IP addr for the laptop. – icelava Sep 9 '09 at 14:00

If IP is statically assigned maybe your router has the filtering by MAC address switched on. Different laptop = different MAC address of network card.

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the router has the new laptop's MAC address in its ARP table; there is no MAC address filtering. – icelava Sep 9 '09 at 13:59

Did you change the listening port on the new laptop? Follow this KB article for instructions:

KB 306759

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No, it's a new laptop and I did not adjust that; it is still 3389 which i can connect fine within the home LAN. – icelava Sep 9 '09 at 13:27

Turn the firewall back on and try again and I would also check what options you have set for RDP if you are mixing XP and Vista/Win7 modes.

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up vote 0 down vote accepted

Turns out McAfee Security Center firewall was blocking the port. The version on this laptop is slightly different from my older laptop's and I did not immediately realise there was another feature page that specifically blocks/unblocks ports for untrusted networks (i.e. Internet).

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