PPTP client works under Windows and doesn't work under Linux - what's wrong with it?

[senglory]

I'm trying to use PPTP on my Slackware machine, the corresponding instruction was taken from - https://vexxhost.com/resources/tuto...-vpn-with-pptp-on-linux-centos-ubuntu-debian/

Here's /etc/peers/khan002

pty "pptp VPN.VPN.VPN.VPN --nolaunchpppd"
name a
password a
remotename PPTP
require-mppe-128

Trying to run the PPTP client:

root@porteus:/etc/ppp/peers# pppd call khan002
Couldn't open the /dev/ppp device: No such file or directory
pppd: You need to create the /dev/ppp device node by
executing the following command as root:
   mknod /dev/ppp c 108 0

Ok, issuing mknod and again

root@porteus:/etc/ppp/peers# pppd call khan002

Silence in the answer. Meanwhile, at the client's log I see this:

Dec 28 19:41:39 porteus pppd[1938]: pppd 2.4.9 started by root, uid 0
Dec 28 19:41:40 porteus pptp[1939]: anon log[main:pptp.c:353]: The synchronous pptp option is NOT activated
Dec 28 19:41:40 porteus pppd[1938]: Using interface ppp0
Dec 28 19:41:40 porteus pppd[1938]: Connect: ppp0 <--> /dev/pts/3
Dec 28 19:41:40 porteus pptp[1951]: anon log[ctrlp_rep:pptp_ctrl.c:258]: Sent control packet type is 1 'Start-Control-Connection-Request'
Dec 28 19:41:40 porteus pptp[1951]: anon log[ctrlp_disp:pptp_ctrl.c:781]: Received Start Control Connection Reply
Dec 28 19:41:40 porteus pptp[1951]: anon log[ctrlp_disp:pptp_ctrl.c:815]: Client connection established.
Dec 28 19:41:40 porteus NetworkManager[629]: <info>  [1640979700.7934] manager: (ppp0): new Ppp device (/org/freedesktop/NetworkManager/Devices/3)
Dec 28 19:41:41 porteus pptp[1951]: anon log[ctrlp_rep:pptp_ctrl.c:258]: Sent control packet type is 7 'Outgoing-Call-Request'
Dec 28 19:41:41 porteus pptp[1951]: anon log[ctrlp_disp:pptp_ctrl.c:900]: Received Outgoing Call Reply.
Dec 28 19:41:41 porteus pptp[1951]: anon log[ctrlp_disp:pptp_ctrl.c:938]: Outgoing call established (call ID 34886, peer's call ID 34).
Dec 28 19:42:11 porteus pppd[1938]: Connection terminated.
Dec 28 19:42:11 porteus pppd[1938]: Modem hangup
Dec 28 19:42:11 porteus pppd[1938]: Exit.
Dec 28 19:42:11 porteus pptp[1951]: anon log[callmgr_main:pptp_callmgr.c:245]: Closing connection (unhandled)
Dec 28 19:42:11 porteus pptp[1951]: anon log[ctrlp_rep:pptp_ctrl.c:258]: Sent control packet type is 12 'Call-Clear-Request'
Dec 28 19:42:11 porteus pptp[1951]: anon log[call_callback:pptp_callmgr.c:84]: Closing connection (call state)
Dec 28 19:43:24 porteus dbus-daemon[1344]: [session uid=0 pid=1342] Activating service name='ca.desrt.dconf' requested by ':1.35' (uid=0 pid=1963 comm="mousepad messages ")
Dec 28 19:43:24 porteus dbus-daemon[1344]: [session uid=0 pid=1342] Successfully activated service 'ca.desrt.dconf'

Here's the matching piece of log at the server side:

Dec 28 22:58:30 pptpd[820]: CTRL: Client CLIENT.CLIENT.CLIENT.CLIENT control connection started
Dec 28 22:58:31 pptpd[820]: CTRL: Starting call (launching pppd, opening GRE)
Dec 28 22:58:31 pppd[821]: Plugin pptp.so loaded.
Dec 28 22:58:31 pppd[821]: PPTP plugin version 0.8.5 compiled for pppd-2.4.7
Dec 28 22:58:31 pppd[821]: pppd 2.4.7 started by admin, uid 0
Dec 28 22:58:31 pppd[821]: Using interface ppp10
Dec 28 22:58:31 pppd[821]: Connect: ppp10 <--> pptp (CLIENT.CLIENT.CLIENT.CLIENT)
Dec 28 22:59:01 pptpd[820]: CTRL: Reaping child PPP[821]
Dec 28 22:59:01 pptpd[820]: CTRL: Client pppd TERM sending
Dec 28 22:59:01 pptpd[820]: CTRL: Client pppd finish wait
Dec 28 22:59:01 pppd[821]: Terminating on signal 15
Dec 28 22:59:07 pppd[821]: Connection terminated.
Dec 28 22:59:07 pppd[821]: Modem hangup
Dec 28 22:59:07 pppd[821]: Exit.
Dec 28 22:59:07 pptpd[820]: CTRL: Client CLIENT.CLIENT.CLIENT.CLIENT control connection finished

Now the routing table has additional route

root@porteus:~# ip route
default via 10.0.2.2 dev eth0 proto dhcp metric 100
10.0.2.0/24 dev eth0 proto kernel scope link src 10.0.2.15 metric 100
VPN.VPN.VPN.VPN via 10.0.2.2 dev eth0 src 10.0.2.15
127.0.0.0/8 dev lo scope link

Server - ASUS hardware router with PPTP turned on. Here're its settings https://ibb.co/qx3TjQ2

What did I do wrong and how to correct the settings?