I have been researching to no avail to the fix or source of MS-VPN (PPTP) connection dropping off (always right at 2:20-2.30 minutes). The problem is not consistant, but happens enough to be a real problem.
Background: XP-Pro2 clients to ISA2004-SP2/Win2003-SP1 server via Cisco PIX515E. VPN has worked in the past. No errors on the internal network or ISA side. I can stay connected using other PC's, models. So far, it seems to be Dell specific since if I move my Linksys USB NIC to the Dell the VPN will drop, but it all works from the clone PC fine (never had disconnect). Since others can stay VPN'd for hours & hours then I don't see it being a network/firewall issue. There is no consistancy in the ISP or broadband type. Sniff trace showed nothing.
Already tried many suggestions (changing MTU, there is no ICS running, ports/protocols OK, changing default channel, updating drivers/firmware, pass-thru enabled etc. etc.). The workaround has been to reboot the home router/wireless access point or to go hardwired, then it is OK; however I noticed someitmes even the hard-wired connection now has this problem.
I know this may not be an ISA problem, but before we drop MS-VPN as a client I wondered if anyone here has an idea where next to troubleshoot or if you have seen this problem.
idle time does not apply here (set to never); even if running a ping loop the connection will drop @ 2 minutes. This seems to have the symptoms of a reported issue with Linksys, but since other (non-Dell) PC's can stay connected then it doesn't seem to be the ISA server, network, or the Linksys router itself.
I have seen this symptom twice. One dealt with GRE keep-alives from the remote router. It seems the remote router would go to sleep or stop forwarding keep-alives so the connection would drop; or freeze. The other occurence turned out to be my local (home) Linksys router's DHCP lease time somehow got set to renew every few minutes. Every time it renewed my vpn connection was dropped. Both were issues that were corrected with a firmware upgrade on the Linksys. I have heard of other manufacturers routers having similar issues, that were also fixed with a firmware update.