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ICTVALUE

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PPTP GRE problem SBS 2003

The most common cause for this is that a firewall or router between the VPN server and the VPN client is not configured to allow Generic Routing Encapsulation (GRE) packets (protocol 47). Verify that the firewalls and routers between your VPN server and the Internet allow GRE packets.
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waynewilliams
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Can I point you to this article?

http://support.microsoft.com/kb/555375


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pistolslapper

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GRE is not a port but a protocol (such as tcp).   You dont need to forward GRE, just ensure that it is allowed through your firewall.

Some firewalls list this as "PPTP Passthrough".  If you can post the make and model of your firewall then we might be able to help you further.
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ICTVALUE

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Hi, We are using a Cisco 520 router as firewall.  Any idea how I should enable PPTP Passthrough ?
Ok. If you have an access-list on the external interface you will need to allow gre through on that.

An example would be:

access-list 100 permit gre any any log

If you can post the config of your router I can tell you exactly which access list and how to add the line in the access list.

Just noticed you have already assigned points for this even though it isnt fixed??

Can you post your Cisco config in a new question and post the link to the new question here and I will gladly take a look at it for you.  If you post it here it wont get a response.