quoted from
http://www.howtonetworking.com/vpnsetup.htm
Which ports need to be opened for running VPN
A: PPTP VPN uses TCP Port 1723, IP Protocol 47 (GRE); L2TP: UDP Port 1701;
IPSec: UDP Port 500, Pass IP protocol 50 and 51. Note: 47 is a protocol
number and not TCP port. The protocol name is GRE. It'll make a big
difference when configuring your firewall or router.
--
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Bob Lin, MS-MVP, MCSE & CNE
How to Setup Windows, Network, Remote Access on
http://www.HowToNetworking.com
Networking, Internet, Routing, VPN Troubleshooting on
http://www.ChicagoTech.net
This posting is provided "AS IS" with no warran