分类： Linux

2012.04.10 更新:ubuntu上除了安装，以及xl2tpd的启动脚本以外，本文的配置方法测试可行。采用编译安装可以参考这篇文章。

2011.11.28 更新:CentOS 6 32bit 下xl2tpd,openswan等安装参照这篇文章,xl2tpd的启动脚本参考这篇文章,配置还是照本文的配置就ok(已经做了一些小修改),如果iptables重启后要重新配置一下才好使可以考虑将iptables那段添加到/etc/rc.local里面

先说下我的环境:CentOS 5.4 32bit 安装了Nginx

针对CentOS有L2TP的一键安装包,首先我推荐尝试一下这个安装包,毕竟很方便,但是我RP不好,这个一键包不仅没能让L2TP在我的机器上正确运行,还因为iptables配置不正确导致Nginx出现404,502错误,如果你也遇到了这个问题,可以简单的通过
service iptables stop
来重置并关闭iptables,以修复nginx的404,502错误,接下来再启用iptables就没什么问题了.但是来l2tp也就肯定不能连接了

这篇文章参考了这里,这里,这里,这里和这里的文章,建议一起看看
下面进入正题:

1. 安装必须的包

   yum install -y ppp iptables make gcc gmp-devel xmlto bison flex xmlto libpcap-devel lsof vim-enhanced
   

2. 编译安装OpenSwan

   wget http://www.openswan.org/download/openswan-2.6.24.tar.gz
   tar zxvf openswan-2.6.24.tar.gz
   cd openswan-2.6.24
   make programs install
   

3. 安装xl2tpd

   yum install xl2tpd
   

4. 编辑 /etc/ipsec.conf 注意$vpsip替换成你机器的ip

   config setup
       nat_traversal=yes
       virtual_private=%v4:10.0.0.0/8,%v4:192.168.0.0/16,%v4:172.16.0.0/12
       oe=off
       protostack=netkey
   
   conn L2TP-PSK-NAT
       rightsubnet=vhost:%priv
       also=L2TP-PSK-noNAT
   
   conn L2TP-PSK-noNAT
       authby=secret
       pfs=no
       auto=add
       keyingtries=3
       rekey=no
       ikelifetime=8h
       keylife=1h
       type=transport
       left=$vpsip #改这里
       leftprotoport=17/1701
       right=%any
       rightprotoport=17/%any
   

5. 编辑 /etc/ipsec.secrets注意$vpsip替换成你机器的ip, $mypsk替换成你想要的密钥

   $vpsip %any: PSK "$mypsk"
   

6. 修改/添加 /etc/sysctl.conf

   net.ipv4.ip_forward = 1
   net.ipv4.conf.default.rp_filter = 0
   net.ipv4.conf.all.send_redirects = 0
   net.ipv4.conf.default.send_redirects = 0
   net.ipv4.conf.all.log_martians = 0
   net.ipv4.conf.default.log_martians = 0
   net.ipv4.conf.default.accept_source_route = 0
   net.ipv4.conf.all.accept_redirects = 0
   net.ipv4.conf.default.accept_redirects = 0
   net.ipv4.icmp_ignore_bogus_error_responses = 1
   

7. 让修改后的sysctl.conf生效

   sysctl -p
   

8. 验证ipsec运行状态

   ipsec setup restart
   ipsec verify
   

   输出以下内容ipsec就配置成功了

   Checking your system to see if IPsec got installed and started correctly:
   Version check and ipsec on-path                             	[OK]
   Linux Openswan U2.6.24/K2.6.32.16-linode28 (netkey)
   Checking for IPsec support in kernel                        	[OK]
   NETKEY detected, testing for disabled ICMP send_redirects   	[OK]
   NETKEY detected, testing for disabled ICMP accept_redirects 	[OK]
   Checking for RSA private key (/etc/ipsec.secrets)           	[OK]
   Checking that pluto is running                              	[OK]
   Pluto listening for IKE on udp 500                          	[OK]
   Pluto listening for NAT-T on udp 4500                       	[OK]
   Two or more interfaces found, checking IP forwarding        	[OK]
   Checking NAT and MASQUERADEing
   Checking for 'ip' command                                   	[OK]
   Checking for 'iptables' command                             	[OK]
   Opportunistic Encryption Support                            	[DISABLED]
   

9. 编辑 /etc/xl2tpd/xltpd.conf

   [global]
   ipsec saref = yes
   listen-addr = $vpsip ;服务器地址
   [lns default]
   ip range = 10.1.2.2-10.1.2.254 ;这里改成你想要的ip范围
   local ip = 10.1.2.1 ;这里改成你想要的ip
   refuse chap = yes
   refuse pap = yes
   require authentication = yes
   ppp debug = yes
   pppoptfile = /etc/ppp/options.xl2tpd
   length bit = yes
   

10. 编辑 /etc/ppp/options.xl2tpd

    require-mschap-v2
    ms-dns 8.8.8.8
    ms-dns 8.8.4.4
    asyncmap 0
    auth
    crtscts
    lock
    hide-password
    modem
    debug
    name l2tpd
    proxyarp
    lcp-echo-interval 30
    lcp-echo-failure 4
    

11. 配置用户名,密码:编辑 /etc/ppp/chap-secrets

    # user server password ip
    username * userpass * #改成你的用户名 密码
    

12. 重启xl2tp

    service xl2tpd restart
    

13. 设置iptables,注意$vpsip改成你机器的ip, 最后一行10.1.2.0改成跟你前面设置xltpd.conf时对应的ip

    iptables -A INPUT -p 50 -j ACCEPT
    iptables -A INPUT -p udp -d `ifconfig | grep 'inet addr:'| grep -v '$vpsip' | cut -d: -f2 | awk 'NR==1 { print $1}'` --dport 500 -j ACCEPT
    iptables -A INPUT -p udp -d `ifconfig | grep 'inet addr:'| grep -v '$vpsip' | cut -d: -f2 | awk 'NR==1 { print $1}'` --dport 4500 -j ACCEPT
    iptables -A INPUT -p udp -d `ifconfig | grep 'inet addr:'| grep -v '$vpsip' | cut -d: -f2 | awk 'NR==1 { print $1}'` --dport 1701 -j ACCEPT
    iptables -t nat -A POSTROUTING -s 10.1.2.0/24 -o eth0 -j MASQUERADE
    

14. 保存

    service iptables save
    service iptables restart
    

15. 添加启动项

    chkconfig xl2tpd on
    chkconfig iptables on
    chkconfig ipsec on
    

l2tp配置完成,过程如有疏漏欢迎批评指正

可能的问题及解决方法：

1. iptables Setting chains to policy ACCEPT: security raw nat mangle filter [FAILED] 问题
   http://vps.openzz.com/archives/224

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