Question : Requirements to use CISCO VPN Client 4.0 with a protected DSL router

I'm getting internet access trought a protected DSL router, and, I want to open the necessary ports to make a connection using my Cisco vpn client 4.0....

Right now is possible ping the IP defined to establish the connection; however, the vpn client indicates that is not getting any answer.

Do you know which ports, and any additional setting that should be necessary to do in the DSL in order to make the program works?

Answer : Requirements to use CISCO VPN Client 4.0 with a protected DSL router

Is the VPN client on the inside of your router or is the client out in the public internet and the VPN endpoint is in your network?  

The solution depends on which one.  

Most consumer routers come with an option to allow ipsec passthrough, as ikalmar said.   Linksys is a good example of these types of devices.    

The Cisco VPN client is an ipsec slient, so if this is on the inside network going out to the public, then all you need to do is make sure you have the latest firmware on the router, and make sure IPSEC passthough is enabled.  

If the client is on the outside and you want to connect internally, there are some additional items we need to complete.    

So, I guess my question is, "Is the client on the inside or outside, and if its on the outside, what internal device are you connecting into?"