connection.Up until recently, the only way I could get my Cisco VPN to work was to place my desktop in the DMZ. I really did not like having to do that. After considerable Internet searching, I could not find any information specific to my D-Link model (DIR 625) for allowing access using a Cisco VPN. Most of the information I was able to locate referenced other models and most made reference to making sure ‘VPN pass-through’ is enabled. Well, AFAIK, the DIR 625 does not have a ‘pass-through’ setting. Other information referred to forwarding port 10000 . However, those failed to mention port 10000 is only used when you configure the VPN to use TCP rather than UDP. My configuration was given to me by our network admin and it uses IPSec/UDP. When I tried to change it, the connection no longer worked even while in the DMZ. I could only conclude the target would only accept UDP.
After a couple of hours of experimentation, I was finally able to establish a connection without being in the DMZ. So that others who may happen to fall into the same situation have a solution, I am providing it here.
The very first thing you must do is to open your D-Link Admin screen, click the Advanced tab on top, and open the Inbound Filter on the left. You’ll need to create a new filter using the IP address where your VPN connects to. You can easily find this by looking at your D-Link log right after an unsuccessful connection attempt (you’ll see the blocked attempt). An example of an Inbound Filter is given here but with my IP partially blocked. My source range is for one IP address. Pay attention to the ‘Name’ given, it will be used again.
After saving your inbound filter, you now need to open the Port Forwarding item on the left of your screen. You will then add a new rule to forward UDP ports 500 through mach zehnder modulator5000 65536 to your local machine using the filter created in the previous step. Its actually pretty easy because the filter name will be in the drop-down list for the Inbound Filter item. Take a look at this example screen shot:
Save your settings and you should now be able to use your Cisco VPN connection without resorting to using the DMZ.