Kernel

egrep -i 'l2tp|ppp' .config

CONFIG_L2TP=m

# CONFIG_L2TP_DEBUGFS is not set

CONFIG_L2TP_V3=y

CONFIG_L2TP_IP=m

CONFIG_L2TP_ETH=m

CONFIG_PPP=m

CONFIG_PPP_BSDCOMP=m

CONFIG_PPP_DEFLATE=m

CONFIG_PPP_FILTER=y

CONFIG_PPP_MPPE=m

# CONFIG_PPP_MULTILINK is not set

CONFIG_PPPOE=m

CONFIG_PPPOL2TP=m

CONFIG_PPP_ASYNC=m

# CONFIG_PPP_SYNC_TTY is not set

emerge -av net-dialup/ppp net-dialup/xl2tpd

/etc/xl2tpd/xl2tpd.conf:

[global]
access control = yes

[lac provider]
lns = <authorization_server>
redial = yes
redial timeout = 10
require chap = yes
require authentication = no
name = <your_login>
ppp debug = yes
pppoptfile = /etc/ppp/options.l2tp
require pap = no
autodial = yes

/etc/ppp/options.l2tp:

name <your_login>
remotename l2tp
ipparam provider
connect /bin/true
nodeflate
nobsdcomp
persist
maxfail 0
nopcomp
noaccomp
mru 1460
mtu 1460

 /etc/ppp/chap-secrets:

<your_login >* <your_password>

add to /etc/ppp/ip-up

ip rout add <your_net>/<> via <your_gateway> dev $1

add to /etc/ppp/ip-down

ip rout del <your_net>/<> via <your_gateway> dev $1

/etc/init.d/xl2tpd start

Let's add xl2tpd to default runlevel, using rc-update:

$ sudo rc-update add xl2tpd default