2、/etc/ppp/ options.ppp0配置如下：

#
# Lock the port
#
lock

#
# We don't need the tunnel server to authenticate itself
#
noauth

#
# Turn off transmission protocols we know won't be used
#
nobsdcomp
nodeflate

#
# We want MPPE
#
mppe-40
mppe-128
mppe-stateless

#
# We want a sane mtu/mru
#
mtu 1000
mru 1000

#
# Time this thing out of it goes poof
#
lcp-echo-failure 10
lcp-echo-interval 10

3、/etc/ppp/chap- secrets配置如下：

# Secrets for authentication using CHAP
# client server secret IP addresses

# OUTBOUND CONNECTIONS
# Here you should add your PPP Login and PPP password to connect to your
# provider via pap. The * means that the entry(login and passoword may be
# used for ANY host you connect to.
# Thus you do not have to worry about the foreign machine name. Just
# replace password with your password.
#hostname * password

# PREDIFINED CONNECTIONS
# These are user and password entries for publically accessible call-by-call
# Internet providers in Germany. If they confict with your config, remove them.
# READ_IN_CALLBYCALL_SECRETS

# INBOUND CONNECTIONS
#client hostname 192.168.1.1
a * a *

//指定了vpn客户端连接时的用户名和密码为a/a，最后一个*意思是从/etc/pptpd.conf中指定的ip范围中随机分配一个IP。