1.拓扑图：
备注：因为应用原因，需要在linux2上添加一个公网地址，并且在中间路由设备不受控制的情况下，Linux1能访问到linux2上面的公网地址。
2.基本接口配置：
linux1:192.168.10.1/24
linux2:192.168.20.2/24
R1:
interface FastEthernet0/0
ip address 192.168.10.10 255.255.255.0
no shutdown
!
interface FastEthernet0/1
ip address 192.168.20.10 255.255.255.0
no shutdown
3.路由配置：
linux1网关:192.168.10.10
linux2网关:192.168.20.10
R1：只有直连路由
4.单网卡多地址配置：
cp /etc/sysconfig/network-scripts/ifcfg-eth0 /etc/sysconfig/network-scripts/ifcfg-eth0:0
vi /etc/sysconfig/network-scripts/ifcfg-eth0:0
# Advanced Micro Devices [AMD] 79c970 [PCnet32 LANCE]
DEVICE=eth0:0
BOOTPROTO=none
ONBOOT=yes
HWADDR=00:0c:29:08:48:63
NETMASK=255.255.255.252
IPADDR=202.100.2.2
TYPE=Ethernet
USERCTL=no
IPV6INIT=no
PEERDNS=yes
[root@ams ~]# service network restart
正在关闭接口 eth0： [确定]
关闭环回接口： [确定]
弹出环回接口： [确定]
弹出界面 eth0： [确定]
[root@ams ~]# ping 202.100.2.2
PING 202.100.2.2 (202.100.2.2) 56(84) bytes of data.
64 bytes from 202.100.2.2: icmp_seq=1 ttl=64 time=0.124 ms
--- 202.100.2.2 ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 0.124/0.124/0.124/0.000 ms
[root@ams ~]# ping 192.168.10.10
PING 192.168.10.10 (192.168.10.10) 56(84) bytes of data.
64 bytes from 192.168.10.10: icmp_seq=1 ttl=255 time=70.6 ms
--- 192.168.10.10 ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 70.629/70.629/70.629/0.000 ms