Symptoms: VPN apparently works fine inside of firewall/router. When connecting from outside, you can get through and authenticate one time, but subsequent times, even days later, you nearly always cannot. You see "Connecting to X.X.X.X" as expected, then "Verifying Username and Password" as expected, but you do not connect, and it finally asks if you want to redial in 60-seconds. Error is 721 "The remote computer did not respond."
I see no entries in the logfile (C:\Winnt\system32\logfiles\iaslog.log) after a connection attempt unless the person successfully authenticates, even with logging set to maximum.
Router: DLink DI-524 with TCP1723 and GRE47 forwarded to private address. This is replacing a Netgear router which also only connected part of the time, but Netgear 2nd Level support said PPTP pass-through may work but is not supported! (D-Link swears this model supports PPTP pass-through, and their 2nd level person kept saying "it should work"... Is there a 3rd level support tier??)
Server: Win2K Server.
Static IP of 192.168.1.4
There was an "Internal" IP of 192.168.1.210 per RRAS IP Routing General Properties in addition to loopback - was operational, but had these sympoms - I've since removed it, have same symptoms and it won't let me add it back
DHCP Relay Agent enabled (at this moment: 8 requests received, 0 requests discarded, 0 replies received or discarded)
RRAS Properties: Enable computer as a Router, LAN routing only, Remote Access Server enabled
Windows Authentication, IP Routing Enabled, and Allow IP-based remote access and demand-dial connections enabled
IP Address assignment from static address pool (same private LAN, with a range not issued by LAN DHCP server specifically 192.168.1.210-229. On the IP assignment block of RRAS Property's IP tab, it put in 192.168.1.192 next to that range automatically?)
No difference when I changed it to assign addresses using DHCP.