pptp - 'Administrative Shutdown'. Error code is 0, Cause code is 0

Question

i need connect trought pptp on my ubuntu 16.10, i have this configuration (works perfectly into my raspberry)

/etc/ppp/peers/myconn

pty "pptp pptpvpn.ams01.softlayer.com --nolaunchpppd --debug"
name xxxx
password xxxx
remotename PPTP
require-mppe-128
require-mschap-v2
refuse-eap
refuse-pap
refuse-chap
refuse-mschap
noauth
debug
persist
maxfail 0

/etc/ppp/ip-up.d/myconn (755)

#!/bin/sh
[ "$IFACE" != "ppp0" ] || exit 0
sudo /sbin/route add -net 10.104.236.0 netmask 255.255.255.0 dev ppp0

After launch pon myconn i have this error:

pppd[6841]: pppd 2.4.7 started by ubuntu, uid 0
pppd[6841]: using channel 53901
pppd[6841]: Using interface ppp0
pppd[6841]: Connect: ppp0 <--> /dev/pts/2
pptp[6843]: anon log[main:pptp.c:350]: The synchronous pptp option is NOT activated
pptp[6868]: anon log[ctrlp_rep:pptp_ctrl.c:259]: Sent control packet type is 1 'Start-Control-Connection-Request'
pptp[6868]: anon log[ctrlp_disp:pptp_ctrl.c:781]: Received Start Control Connection Reply
pptp[6868]: anon log[ctrlp_disp:pptp_ctrl.c:815]: Client connection established.
pppd[6841]: sent [LCP ConfReq id=0x1 <asyncmap 0x0> <magic 0xc44e461e> <pcomp> <accomp>]
pptp[6868]: anon log[ctrlp_rep:pptp_ctrl.c:259]: Sent control packet type is 7 'Outgoing-Call-Request'
pptp[6868]: anon log[ctrlp_disp:pptp_ctrl.c:900]: Received Outgoing Call Reply.
pptp[6868]: anon log[ctrlp_disp:pptp_ctrl.c:939]: Outgoing call established (call ID 44491, peer's call ID 59622).
pppd[6841]: sent [LCP ConfReq id=0x1 <asyncmap 0x0> <magic 0xc44e461e> <pcomp> <accomp>]
pppd[6841]: message repeated 5 times: [ sent [LCP ConfReq id=0x1 <asyncmap 0x0> <magic 0xc44e461e> <pcomp> <accomp>]]
pptp[6868]: anon log[ctrlp_disp:pptp_ctrl.c:975]: Call disconnect notification received (call id 59622)
pptp[6868]: anon log[ctrlp_error:pptp_ctrl.c:207]: Result code is 3 'Administrative Shutdown'. Error code is 0, Cause code is 0
pptp[6868]: anon log[call_callback:pptp_callmgr.c:84]: Closing connection (call state)
pppd[6841]: Script pptp pptpvpn.ams01.softlayer.com --nolaunchpppd --debug finished (pid 6842), status = 0x0
pppd[6841]: Modem hangup
pppd[6841]: Connection terminated.

This Linux is under NAT, ufw is disabled and iptables accept all in all direction...someone can help me? I have no idea

Answer 1

This is not configuration level problem. Probably you have configured your PPPD just fine as the configuration works on another device without NAT.

You should not use PPTP at all as it is has come obsolete due to several security problems. You really should use some secure alternative instead, like OpenVPN. If you still want to use PPTP...

The problem you have is most likely that you don't have PPTP Passthrough on your NAT:

PPTP uses a TCP channel on port 1723 for control and the GRE protocol to encapsulate data and create a VPN tunnel. The issue isn’t really PTPP itself but GRE; GRE doesn’t use ports. Since a requirement of NAT is that the connection must use an IP address and port number it doesn’t work with GRE. This is what PTPP passthrough addresses.

For PPTP you need the following openings in the firewall:

• IP Protocol=TCP, TCP Port number=1723 (Used by PPTP control path)
• IP Protocol=GRE (value 47) (Used by PPTP data path)

For GRE, you need a router with support for Enhanced GRE header Passthrough. In the router configuration this could be a setting named PPTP or IPsec passthrough.

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The 3 'Administrative Shutdown' is just a normal result code from PPTP Clients pptp_ctrl.c (PPTP control connection) case PPTP_CALL_CLEAR_NTFY after receiving pptp_call_clear_rqst from void pptp_call_close(). It doesn't give any extra information; other than the connection is closed.