I am having a very strange issue with PPTP between two routerboards. I am connecting two networks using RouterOS PPTP VPN on both sides. This setup worked very well for about 3 months. Transfer speeds were good and very stable connection between the two networks. Now it seems to be broken without any configuration changes on the Mikrotiks.

My remote side can download okay and speeds are very fast. My remote uploads are much slower than they used to be and SCP from remote network to home network is not working at all. Packets seem to get dropped and SCP connection attempts are constantly aborted. I checked the firewall on both sides, and nothing has changed. PPTP settings are the same as well.

I also tried to connect directly to PPTP server through windows and same behavior happens. I read a post at http://forum.mikrotik.com/viewtopic.php ... tp#p199671 and it said PPTP can break if packets are transmitted out of order. I'm not sure if my problem is exactly what was described in that post. And, I am not sure where to begin troubleshooting this. Ideas anybody?

I did some troubleshooting last night which included calling the ISP. There were also other drops where ICMP requests would just stop working and the internet would just drop out alltogether. ISP suggested to bypass the router and attempt connections directly through the cable modem. I didn't believe them at first, but thought I would try. When I bypassed the RB450, the VPN connection worked very well just as before. I'm doing a permanent bypass of the Mikrotik w/ a Linksys until I can get another Tik in place.

did you have a solution for this problem i have a similar one?

Adjust your MTU and MSS values to something that fits into the VPN link. The wiki shows how to do this in the Ethernet FAQ (the same issue is common with PPPoE links, and any other links that introduce extra headers and reduce payload sizes).

You've re-opened at least a dozen threads with the same FAQ. I find that sort of rude.

ok Mtu i can adjust from the pptp connection but how can i adjust the MSS

i tried alot to change the MTU and MRU but didn't work

http://wiki.mikrotik.com/wiki/Manual:Ro ... _Questions
Also try and adjust the MTU on the Windows PPTP interface in case you're blocking path discovery in your firewall filters.