A Problem with Router dropping Windows Terminal through VPN

I am having a problem with my Microtic. There is a VPN running from one section of the network (through the Microtic) to another section. The VPN stays up and outside of the VPN one side can ping the other. Windows Terminal will run for a few Mins and then just get killed. We have done testing that shows it only happens when the connection goes through the Microtic.
Has anyone else experienced this problem with Windows terminal and the Microtics?

Are you accidently NAT’ting across the VPN? If so, then the terminal server may be seeing multiple users coming from the same IP and dropping the older one. Make sure your SRC-NAT or MASQ rule isn’t matching traffic across the VPN.

what kind of vpn is it? pptp, l2tp, ipsec?

It is 2 Sonic Wall VPN routers connecting to each other with a microtic routing between the 2 networks. I will get more info on the Sonic wall VPN settings and post them shortly.

The VPN uses ipsec.

I use terminal services extensively via mikrotik routers.

my pc => my mt router => internet => client mt router => windows server rdp session

This does work, although I’m running PPTP but I did need to play with the MTU/MSS settings.

Are you by any chance using Vista? I needed to make a change there as well else the VPN would drop exactly 5 minutes later. On the nose!

We have had problems like that… the TS window opens but the screen remains black.

This was resolved changing the MTU in mangle rules.

Greetings

Mine is this;

chain=forward action=change-mss new-mss=1442 tcp-flags=syn out-interface=adsl protocol=tcp

I have found out that this setting does vary from DSL line to DSL line. The other day I needed to drop this this all the way down to 1400 at a client whereas on my home router, I haven’t even made any changes. This setting is from my office router.