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I use my a Windows Server 2008 R2 workstation as a VPN client to a Windows 2003 RRAS VPN host. It has worked flawlessly for many months.

All of sudden, rasClient stops connecting and throws:

Error 651:  The modem (or other connecting device) has reported an error

Here are some steps I have already taken:

  1. Host VPN server is still working; can connect to it from another machine outside the client's router
  2. The client is "outside" the router firewall in a DMZ, it can't be reached on port 1723 even though both router and Windows firewalls suggest it should be open (not sure if this matters).

The ISP has an annoying habit of occasionally pushing down router firmware updates to my modem/router. I am also wondering if the ISP (a very large company) could have decided to block VPN traffic from home subscribers?

I am looking for a clear description of what must be open/accessible on my client, and what additional steps I might take to verify these conditions.

share|improve this question
If your ISP is Charter, you can bet its blocked... – Fergus Mar 19 '12 at 4:26
what ip ranges are the server/client on? they should be differnt but sometimes if you use defult DHCP they can be the same. – t1nt1n Mar 19 '12 at 6:18

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