As of 5.8, it appears that Conntrack and SNAT are unable to track multiple GRE tunnels to the same host. This problem manifests is self as multiple users behind a MikroTik NAT router are unable to PPTP VPN into the same remote server.
more information is available in this thread:
http://forum.mikrotik.com/viewtopic.php?f=2&t=56685
Additionally the netfilter mailing list has a lot of discussion about this topic when they introduced the nf_conntrack_pptp module
Re: Feature Request: GRE NAT Tracking (PPTP)
Such feature already exist.
Code: Select all
/ip firewall service-port enable pptp
Re: Feature Request: GRE NAT Tracking (PPTP)
I thought I had that enabled during my testing. I will go back and try it again. Thank you.