PPtP
I never got this working there was some kind of authentication issue between the client and server but there are almost not diagnostic messages here. Old software doesn't feel good.
Server
Was done on Gentoo.
emerge net-vpn/pptpd
cat << 'EOF' > /etc/pptpd.conf
# /etc/pptpd.conf
option /etc/ppp/options.pptpd
logwtmp
# 10.202.254.128
localip 172.16.45.5
remoteip 172.16.45.100-200
EOF
cat << 'EOF' > /etc/ppp/options.pptpd
name pptpd
refuse-pap
refuse-chap
refuse-mschap
require-mschap-v2
require-mppe-128
ms-dns 1.1.1.1
ms-dns 1.0.0.1
#proxyarp
lock
nobsdcomp
novj
novjccomp
nologfd
# May not be valid / needed
noipx
mtu 1490
mru 1490
EOF
cat << 'EOF' > /etc/ppp/chap-secrets
# /etc/ppp/chap-secrets
# Secrets for authentication using CHAP
# client server password IP addresses
test-user * test-password *
EOF
sysctl -w net.ipv4.ip_forward=1
Client
This was on Fedora 29
dnf install pptp -y
cat << 'EOF' > /etc/ppp/chap-secrets
# /etc/ppp/chap-secrets
# client server password IP addresses
test-user * test-password *
EOF
cat << 'EOF' > /etc/ppp/peers/test-connection
pty "pptp 10.202.254.128 --nolaunchpppd"
name test-user
remotename PPTP
require-mppe-128
file /etc/ppp/options.pptp
ipparam test-connection
EOF
pppd call test-connection
tail -f /var/log/messages