I can't VPN with GPRS anywhere!

[sorci]

I'm trying to VPN using GPRS to several networks which I have access to but I can't seem to be able to VPN them with my PDA2K. I can VPN them easily with no special configuration with my XP.

My i-mate keeps trying "Connectioning XX VPN..." and then aborts after about half a minute saying to check the username and password. The username and password are correct.

I called my cellular provider and they said that I should be able to connect to a VPN only if 'UDP Encapsulation' is defined on the VPN server?!?!? Well.. What is this thing? I'm trying to connect to big corp VPN, they wouldn't even listen to 'special requests'. I tried to connect to 4 different VPNs and I could not connect to any single one of them!

I really need that VPN connection via GPRS with my PDA2K. Any help would be more than appreciated. Maybe a different client than the built in VPN client of the WM2003SE ?

Thanks in advance.
Sorci

[sorci]

bump for help. this gotta be a common prob. :(

[Jamz]

Your GPRS connection will be subject to some form of NAT (Network Adress Translation) (http://searchnetworking.techtarget.com/sDefinition/0,,sid7_gci214107,00.html) through your provider. VPNs don't get along well with NAT as the firewall doing the address translation modifies the packet header after it has had it's hash value calculated by the client (in this case your PDA). The receiving firewall will reject the packet as the hash values for the (now modified) packet don't match.

UDP encapsulation gets around this by encapsulating the encrypted and authenticated (secure) packet in a UDP packet which will be happily modified by the NAT'ing firewall. The receiving firewall will decapsulate(is that even a word?) the UDP packet and process secure packet inside as normal.

James

[sorci]

Thanks a lot Jamz for the thorough detailed info. I appreciate it.
So what's the fix? I tried several other VPNs and was unable to access them as well.. I can't just call all these providers and make some strange requests for a 'one guy with a pda2k and a gprs connection' that wants them to change their VPNs, enabling or disabling protocols or port.

Any other solution?

[d-o-h!]

Any other solution?

Are you sure you're using the built-in VPN client in Windows, and not something like a Cisco VPN client?

You could try something like the Movian VPN client (not sure this is still made). I've used this previously with a Cisco VPN and it is fully configurable to handle multiple VPN types.

[rascom]

I've got a similar problem. Am trying to set up a temporary GPRS connection into my work LAN (I work for myself but 2nd child due shortly so want to be able to connect in from home for a couple of weeks only). I've got MS Win2000 Server set up to accept incoming VPN connections and it works fine on a dial-up connection but refuses to authenticate my username/pasword whenever I try to get the GPRS working.

As it's only going to be used for a short period of time, I'm loathe to spend out on any specific hardware/software but if anyone's got any suggestions, I'd be grateful.

If it helps, the LAN is behind a Netgear DG834GT ADSL modem/router/firewall and VPN PPTP and IPSEC are allowing in and out on it. The server is on a static IP address in the range 192.168.99.x.

[Beridor]

With O2 you have to aks for VON connectivity to be enabled and connect to vpn.o2.co.uk instead of mobile.o2.co.uk. (by the way you can't access the web whilst connected to the vpn.o2.co.uk AP)

I suspect that most providers have simalair requirements

Dave