VPN help: error 721, the remote computer did not respond

Enabled port 1723 on what?  I'm assuming a router/firewall of somekind.  Does it allow ipsec passthru.  You also need to enable GRE 47.  On some routers this is IP protocol 47.  NOT PORT 47.

What equipment are you using for the VPN? I assume all details are setup correctly in the VPN connection.  Correct Target IP etc.?

port 1723 and ipsec are enabled.  I didn't find GRE 47 or IP protocol 47. Can you give me some detail on how to enable it?

Sorry no can't tell you how to enable, not all routers have it, and I don't know what equipment you are using.  Does your Router have a VPN passthru option?  What is the equipment you are using?  If your router has a VPN passthru option that will enable the necessary ports and protocols.


Difficult to say without fully knowing your setup.

my router is sonicWall TZ170(Sonic OS Standard 2.2)

Well according to the specs of that device, it supports VPN passthru.  Have you found the option to enable this?

Unfortunately I don't know the sonicwalls interface so I can't help you, but if it supports it there should be an option somewhere to enable Passthru.

Once that is enabled, then assuming the VPN client is correct it should work.

Not sure if this will help but it is a pdf detailing the setting up of VPN using sonic products.

http://www.sonicwall.com/services/pdfs/Configuring_GroupVPN_GVC_SonicOS_Standard.pdf

Basically I'm assuming that everything is fine on the client end, and the VPN host end.  In which case there is something blocking VPN packets.

Find that and you are sorted.

Unfortunately I don't know your gear well enough to point you in the right direction, sorry.  

It is not necessary to add GRE (IP protocol 47) to the SonicWALL in order to support PPTP pass-through (either for a client connecting to a server on the Internet, or clients on the WAN connecting to a server on the LAN side). GRE is handled automatically as needed whenever a PPTP connection is established.