搭建L2TP over IPSec VPN

搭建L2TP over IPSec VPN1.服务器安装软件yum install openswan xl2tpd ppp2.服务器配置文件/etc/ipsec.conf修改内容如下，VPN客户端内网

搭建L2TP over IPSec VPN

1.服务器安装软件

yum install openswan xl2tpd ppp

2.服务器配置文件/etc/ipsec.conf修改内容如下，VPN客户端内网地址网段自定义，公网地址为服务器公网地址

config setup    protostack=netkey    dumpdir=/var/run/pluto/    nat_traversal=yes    virtual_private=%v4:VPN客户端内网地址网段/24conn L2TP-PSK-NAT    rightsubnet=vhost:%priv    also=L2TP-PSK-noNAT    conn L2TP-PSK-noNAT    authby=secret    pfs=no    auto=add    keyingtries=3    dpddelay=30    dpdtimeout=120    dpdaction=clear    rekey=no    ikelifetime=8h    keylife=1h    type=transport    left=公网地址    leftprotoport=17/1701    right=%any    rightprotoport=17/%any

3.设置VPN共享密钥，服务器配置文件/etc/ipsec.secrets修改内容如下，密钥自定义

%any: PSK "密钥"

4.修改服务器内核参数，服务器配置文件/etc/sysctl.conf修改或者添加内容如下

net.ipv4.ip_forward = 1net.ipv4.conf.default.rp_filter = 0net.ipv4.conf.all.rp_filter = 0net.ipv4.conf.all.send_redirects = 0net.ipv4.conf.default.send_redirects = 0net.ipv4.conf.all.accept_redirects = 0net.ipv4.conf.default.accept_redirects = 0net.core.xfrm_larval_drop = 1

5.服务器执行命令，修改内核参数立即生效

sysctl -p

6.执行脚本

for each in /proc/sys/net/ipv4/conf/*do    echo 0 > $each/accept_redirects    echo 0 > $each/send_redirectsdone

7.防火墙添加规则

iptables -t nat -A POSTROUTING ! -s 127.0.0.1/8 -j MASQUERADEiptables -I FORWARD -p tcp -m tcp --tcp-flags SYN,RST SYN -j TCPMSS --clamp-mss-to-pmtu

8.服务器启动ipsec服务

• RHEL/CentOS 6系列

service ipsec start

• RHEL/CentOS 7系列

systemctl start ipsec

9.服务器检查ipsec服务

ipsec verify

运行结果显示类似如下，除两行不是[OK]表明正常：

Verifying installed system and configuration filesVersion check and ipsec on-path                         [OK]Libreswan 3.15 (netkey) on 3.10.0-123.9.3.el7.x86_64Checking for IPsec support in kernel                    [OK] NETKEY: Testing XFRM related proc values         ICMP default/send_redirects                    [OK]         ICMP default/accept_redirects                  [OK]         XFRM larval drop                               [OK]Pluto ipsec.conf syntax                                 [OK]Hardware random device                                  [N/A]Two or more interfaces found, checking IP forwarding    [OK]Checking rp_filter                                      [OK]Checking that pluto is running                          [OK] Pluto listening for IKE on udp 500                     [OK] Pluto listening for IKE/NAT-T on udp 4500              [OK] Pluto ipsec.secret syntax                              [OK]Checking 'ip' command                                   [OK]Checking 'iptables' command                             [OK]Checking 'prelink' command does not interfere with FIPSChecking for obsolete ipsec.conf options                 [OK]Opportunistic Encryption                                [DISABLED]

10.服务器配置文件/etc/xl2tpd/xl2tpd.conf修改内容如下

[global]ipsec saref = yes[lns default]ip range = VPN客户端内网起始IP地址-VPN客户端内网结束IP地址local ip = VPN服务器内网IP地址require chap = yesrefuse pap = yesrequire authentication = yesname = VPN Serverppp debug = yespppoptfile = /etc/ppp/options.xl2tpdlength bit = yes

11.服务器配置文件/etc/ppp/options.xl2tpd修改内容如下

ipcp-accept-localipcp-accept-remoterequire-mschap-v2ms-dns DNS服务器地址1ms-dns DNS服务器地址2 noccpnoipv6authcrtsctsidle 1800nodefaultroutedebuglocknoproxyarpconnect-delay 5000lcp-echo-interval 30lcp-echo-failure 3logfile /var/log/xl2tpd.log

12.服务器启动xl2tpd服务

• RHEL/CentOS 6系列

service xl2tpd start

• RHEL/CentOS 7系列

systemctl start xl2tpd

13.服务器配置文件/etc/ppp/chap-secrets添加账号，格式如下

账号 * 密码 *

Windows 7及以上系统连接L2TP over IPSec VPN不稳定解决方法：

• 新建.reg后缀名的文件，将下列内容添加至该文件并双击运行，之后重启电脑：*

Windows Registry Editor Version 5.00[HKEY_LOCAL_MACHINE/SYSTEM/CurrentControlSet/Services/PolicyAgent]"AssumeUDPEncapsulationContextOnSendRule"=dword:00000002