l2tp провайдера раздать по локалке

/etc/xl2tpd/xl2tpd.conf:
[global]
access control = yes
[lac <xl2tp-server>]
lns = <xl2tp-server>
redial = yes
redial timeout = 5
require chap = yes
require authentication = no
name = <your_username>
ppp debug = yes
pppoptfile = /etc/ppp/options.xl2tpd
require pap = no
autodial = yes

/etc/ppp/options.xl2tpd:

name <your_username>
remotename l2tp
ipparam <ISP>
connect /bin/true
nodeflate
nobsdcomp
persist
maxfail 0
nopcomp
noaccomp
defaultroute
replacedefaultroute

/etc/ppp/chap-secrets 

<your_username> * <your_password>

До старта демона
route add -host <host xl2tp-server> gw <default-gw>
route add -host <dns-server-1> gw <default-gw>
route add -host <dns-server-2> gw <default-gw>