server：CentOS5.8
ip：172.16.8.11 Gateway：172.16.8.1
ip：10.120.6.78 Gateway：10.120.6.1
网卡配置：
eth0 point： [root@localhost ~]# cat /etc/sysconfig/network-scripts/ifcfg-eth0
# Intel Corporation Gigabit Network Connection
DEVICE=eth0
BOOTPROTO=none
HWADDR=:FB::B0:F3:CE
ONBOOT=yes
IPADDR=172.16.8.11
NETMASK=255.255.255.0
GATEWAY=172.16.8.1
TYPE=Ethernet ech1 point：
[root@localhost ~]# cat /etc/sysconfig/network-scripts/ifcfg-eth1
DEVICE=eth1
BOOTPROTO=none
HWADDR=:FB::B0:F3:CF
ONBOOT=yes HOTPLUG=no
IPADDR=10.120.6.78
NETMASK=255.255.254.0
打开转发：
[root@localhost ~]# echo > /proc/sys/net/ipv4/ip_forward 不知道这一步是不是有必要我临时打开了。
配置路由表：
[root@localhost ~]# cat /etc/iproute2/rt_tables
# reserved values
local
main default
252 net0
251 net1
unspec
#
# local
#
# inr.ruhep
[root@localhost ~]#
使用ip route添加默认路由：
ip route add 127.0.0.0/ dev lo table net1
ip route add default via 172.16.8.1 dev eth0 src 172.16.8.11 table net1
ip rule add from 172.16.8.11 table net1 ip route add 127.0.0.0/ dev lo table net0
ip route add default via 10.120.6.1 dev eth1 src 10.120.6.78 table net0
ip rule add from 10.120.6.78 table net0 ip route flush table net1
ip route flush table net0
注意测试的时候指定源地址：
[root@localhost ~]# ping -I 172.16.8.11 www.baidu.com
PING www.a.shifen.com (220.181.111.188) from 172.16.8.11 : () bytes of data.
bytes from 220.181.111.188: icmp_seq= ttl= time=8.69 ms
bytes from 220.181.111.188: icmp_seq= ttl= time=8.57 ms --- www.a.shifen.com ping statistics ---
packets transmitted, received, % packet loss, time 999ms
rtt min/avg/max/mdev = 8.575/8.636/8.698/0.111 ms
[root@localhost ~]# ++++++++++++++++++++++++++++++++++++++++++++++++++
[root@localhost ~]# ping -I 10.120.6.78 10.11.240.22
PING 10.11.240.22 (10.11.240.22) from 10.120.6.78 : () bytes of data.
bytes from 10.11.240.22: icmp_seq= ttl= time=10.9 ms
bytes from 10.11.240.22: icmp_seq= ttl= time=10.6 ms
bytes from 10.11.240.22: icmp_seq= ttl= time=10.6 ms
bytes from 10.11.240.22: icmp_seq= ttl= time=10.7 ms
bytes from 10.11.240.22: icmp_seq= ttl= time=10.8 ms
bytes from 10.11.240.22: icmp_seq= ttl= time=10.5 ms
bytes from 10.11.240.22: icmp_seq= ttl= time=10.6 ms --- 10.11.240.22 ping statistics ---
packets transmitted, received, % packet loss, time 6002ms
rtt min/avg/max/mdev = 10.525/10.727/10.910/0.172 ms
[root@localhost ~]#
PS：10.11.240.22 是我们的ipsec对端，是能够通过10.120.6.78 访问的。