参考
http://blog.51yip.com/linux/1795.html
说到VPN，就会想到google，满心的疼。以前写过一篇关于vpn的文单，请参考：centos5.5 vpn 安装配置详解，这篇文章是讲pptp的，pptp走的是tcp，l2tp走的是udp。pptp用的时间长了，就会间断性的被墙。
一，安装xl2tpd openswan
- # yum install xl2tpd openswan ppp
如果没有安装包，安装epel源，在这里不多说了，在博客里面搜索一下
二，配置ipsec
1，配置ipsec.conf
# cat /etc/ipsec.conf version
config setup
protostack=netkey
logfile=/var/log/pluto.log
listen=172.16.11.2
dumpdir=/var/run/pluto/
virtual_private=%v4:10.0.0.0/,%v4:192.168.0.0/,%v4:172.16.0.0/,%v4:25.0.0.0/,%v4:100.64.0.0/,%v6:fd00::/,%v6:fe80::/ conn L2TP-PSK-NAT
rightsubnet=vhost:%priv
also=L2TP-PSK-noNAT conn L2TP-PSK-noNAT
authby=secret
pfs=no
auto=add
keyingtries=
rekey=no
ikelifetime=8h
keylife=1h
type=transport
left=172.16.11.2
leftprotoport=/
right=%any
rightprotoport=/%any
2，设置 PSK共享密钥
# cat /etc/ipsec.secrets 172.16.11.2 %any: PSK "sec123"
# vim /etc/sysctl.conf
net.ipv4.ip_forward = //将0改为1 # sysctl -p //立马生效
开启转发
# vim /etc/ipsec.d/net.sh //加入以下内空
for each in /proc/sys/net/ipv4/conf/*
do
echo 0 > $each/accept_redirects
echo 0 > $each/send_redirects
done # chmod +x /etc/ipsec.d/net.sh
# sh /etc/ipsec.d/net.sh
4，启动ipsec，并验证
# service ipsec start # 验证
# ipsec verify Verifying installed system and configuration files Version check and ipsec on-path [OK]
Libreswan 3.15 (netkey) on 2.6.-573.22..el6.x86_64
Checking 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]
Checking rp_filter [OK]
Checking that pluto is running [OK]
Pluto listening for IKE on udp [OK]
Pluto listening for IKE/NAT-T on udp [OK]
Pluto ipsec.secret syntax [OK]
Checking 'ip' command [OK]
Checking 'iptables' command [OK]
Checking 'prelink' command does not interfere with FIPS [PRESENT]
Checking for obsolete ipsec.conf options [OK]
Opportunistic Encryption [DISABLED]
ipsec verify如果没有出现failed，就说明ipsec安装成功了。
三，配置xl2tpd
# cat /etc/xl2tpd/xl2tpd.conf
[global]
ipsec saref = no
listen-addr = 172.16.11.2
[lns default]
ip range = 192.168.100.128-192.168.100.254
local ip = 172.16.11.2
require chap = yes
refuse pap = yes
require authentication = yes
name = LinuxVPNserver
ppp debug = yes
pppoptfile = /etc/ppp/options.xl2tpd
length bit = yes
1，配置options.xl2tpd
# cat /etc/ppp/options.xl2tpd
ipcp-accept-local
ipcp-accept-remote
ms-dns 8.8.8.8
noccp
auth
crtscts
idle
mtu
mru
nodefaultroute
debug
lock
proxyarp
connect-delay
require-mschap-v2
asyncmap
modem
name l2tpd
lcp-echo-interval
lcp-echo-failure
2，添加VPN用户
- # cat >>/etc/ppp/chap-secrets<<EOF
- > vpnuser * 111111 *
- > EOF
五，配置iptables snet
- # iptables -t nat -I POSTROUTING 1 -j SNAT -s 192.168.0.0/24 --to 192.168.10.202
- # iptables-save
六，加入开机启动
- # chkconfig ipsec on
- # chkconfig xl2tpd on
- # cat >>/etc/rc.local<<EOF
- sh /etc/ipsec.d/net.sh
- EOF