因为公司的需要，现在又追加了一个网段A：10.4.1.*/16,而公司原有域为B：10.2.1.*/16，为了使两个网段能够通信，本文的目的就在Ubuntu下设置路由
使两个网段可以互相通信。
1、ubuntu机器配置为双网卡，分别连接两个网段。
#router@proxy:/etc/network$ sudo vi interfaces
dd
# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).
# The loopback network interface
auto lo
iface lo inet loopback
# The primary network interface
auto eth0
iface eth0 inet static
address 10.2.1.216
netmask 255.255.0.0
network 10.2.0.0
broadcast 10.2.255.255
gateway 10.2.1.218
# dns-* options are implemented by the resolvconf package, if installed
dns-nameservers 211.93.80.129 211.94.65.97 211.98.4.1
auto eth1
iface eth1 inet static
address 10.4.1.216
netmask 255.255.0.0
network 10.4.0.0
broadcast 10.4.255.255
gateway 10.4.1.10
dns-nameservers 211.93.80.129 211.94.65.97
iface dsl-provider inet ppp
provider dsl-provider
2、打开包转发
编辑/etc/sysctl.conf
把
net.ipv4.ip_forward = 0
改成
net.ipv4.ip_forward = 1
