PPTP server behind 1:1 nat

RouterOS General
1

I have a MT pptp-client with static public ip address on its wan, trying to connect a MT pptp-server behind a 1:1 natted ISP router.

Client hangs on “link established”
After first data exchange, client hangs in

sent LCP ConfReq  id=0x20
<mru 1450>
<magic 0x35bc8ec0>
LCP open

port 1723 TCP and GRE protocol accept rules are ok on input chain of server

Is the issue caused by NAT on server side ?

Other MT pptp servers are working fine when public ip is configured directly on wan interface (not natted) .

2

Tried also to work with /ip firewall service-port pptp helper, nothing changed (perhaps service-port is used for forward ?)
Don’t know what else to try…

3

The ISP device, does it have such pptp helper checkbox?
Use sniffer tool on both ends to see which side sends/receives GRE protocol packets. They might get blocked somewhere in between , probably on ISP router

4

The ISP device is a silly Vodafone Station with MT PPtP server (RB3011) in its DMZ address.
I’m able to connect my RB3011 from my iPhone L2TP/ipsec client as well as bring up a GRE/ipsec static tunnel from a remote RB3011
No luck with third 3011 running PPTP client stuck in situation reported…
Is there perhaps a problem running PPTP server at same time with a L2TP server or existing GRE ?

5

There is no such problem on the MikroTik router but I know of plenty of problems with NAT and “DMZ” settings in consumer-grade routers.
PPTP on such a NAT router will normally only work on the client side, not when the router is on the server side.

When you are faced with such a router it is better to not use technologies like PPTP (which should be deprecated anyway).
Try to use SSTP instead when you cannot use L2TP/IPsec.