Ubuntu20.04 搭建L2TP+IPsec环境

1 安装

安装l2tp和strongswan。

sudo apt install xl2tpd
sudo apt install strongswan

2 ipsec配置

1）编辑**/etc/ipsec.conf**

conn L2TP-IPSEC
    authby=secret
    auto=add
    keyingtries=3
    ikelifetime=8h
    keylife=1h
    keyexchange=ikev2
    ike=chacha20poly1305-sha512-curve25519-prfsha512
    esp=chacha20poly1305-sha512,aes256gcm16-ecp384,aes256-sha256,aes256-sha1,3des-sha1
    # 连接类型 传输模式transport/隧道模式tunnel
    type=transport
    # 服务器公网地址
    left=10.25.X.X
    # 服务器子网网段
    leftsubnet=10.25.17.0/24[17/1701]
    # 客户端访问地址
    right=%any # right=10.25.16.0/24
    # rightsubnet=10.25.16.0/24[17/%any]
    dpddelay=30s
    dpdtimeout=150s
    dpdaction=clear
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2）编辑**/etc/ipsec.secrets** , 设置ipsec的预共享秘钥

# This file holds shared secrets or RSA private keys for authentication.

# RSA private key for this host, authenticating it to any other host
# which knows the public part.
: PSK "123456"
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3 l2tp配置

编辑**/etc/xl2tpd/xl2tpd.conf**

[global]
ipsec saref = no
debug tunnel = no
debug avp = no
debug network = no
debug state = no
access control = no
rand source = dev
port = 1701
auth file = /etc/ppp/chap-secrets

[lns default]
# 分配给客户端的私有网络地址
ip range = 192.168.100.100 - 192.168.100.254
# 服务器私有网络地址 绑定网卡的实际网络地址
local ip = 192.168.100.210
name = l2tp
pass peer = yes
refuse pap = yes
refuse chap = yes
require authentication = yes
ppp debug = no
# 指定PPP配置文件路径
pppoptfile = /etc/ppp/options.xl2tpd
length bit = yes
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4 ppp配置

1） 编辑PPP配置文件(例如上文中的**/etc/ppp/options.xl2tpd**)。

require-mschap-v2
refuse-mschap
# DNS服务器地址
ms-dns 127.0.0.53
asyncmap 0
auth
crtscts
idle 1800
mtu 1410
mru 1410
hide-password
local
modem
lock
name l2tpd
connect-delay 5000
lcp-echo-interval 30
lcp-echo-failure 4
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2）编辑**/etc/ppp/chap-secrets**，添加VPN访问用户密码

# Secrets for authentication using CHAP
# client        server  secret                  IP addresses
root * root *
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5 重启服务

#重启服务

$sudo service xl2tpd restart
$sudo service ipsec restart

#确认服务状态

$sudo service xl2tpd status
$sudo service ipsec status

6 添加子网路由

当客户端可以连接到VPN服务器时，需要添加路由才可以访问私有网络中的其它机器。

# 添加访问192.168.100网段的路由
route add -net 192.168.100.0/24 netmask 255.255.255.0 gw 192.168.100.1
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