Problem with VPN connections throught a ISA 2006 server

Hi Experts,

My organization has a ISA Server 2006 as a firewall, working with two interfaces, internal and external. We have internal computers establishing VPN connection with other external VPN servers, but when the other VPN end is a Zyxel router/firewall, the VPN can not be established, showing error 619 on the origin (the Windows XP computer trying to establish a PPTP VPN). If we stop the ISA Server and configure our router to work without the ISA Server, this VPN connection is established without problem. We allways use NAT.

Any idea about what's happening with ISA Server?

Thanks in advance.
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SysExpertConnect With a Mentor Commented:
Upgrade the firmware.

I would check all the filters and rules to see what traffic you are blocking.

I hope this helps !
ALso check the relevant logs

david-martiAuthor Commented:
Thanks for your answer.

No, nothing blocks this kind traffic. I can successfully establish VPN with other VPN servers using PPTP ... the only problem is with this Zyxel.
Rob WilliamsConnect With a Mentor Commented:
One thought: make sure NAT-T (NAT-traversal) is enabled on the Zyxel, in its VPN configuration.
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