应一个朋友的需求，另外，觉得实际工程中也可能要用到，因此撰写了关于网络两端网段重叠的处理方法的实例文章。
一、拓扑及网段分布如下：
备注：其中的S2016和S2008在此处是作为PC的功能使用的，S2016的IP是74.40.88.200/24缺省网关指向路由器A 74.40.88.254/24 。S2008的IP是74.40.88.1/28 缺省网关指向路由器C 74.40.88.1/28。此2机器的配置不再列出。图中S3100作为普通交换机使用，未任何配置。
二、不用NAT双向映射的试验结果
备注：此时路由器A所在的网段不能是用74.40.88.1-74.40.88.16范围内的IP地址，因为该范围属于74.40.88.0/28。
配置如下：其中红色部分为关键配置
路由器A：
#sysname AR2810-A
#cpu-usage cycle 1min
#router id 1.1.1.1
#radius scheme system
#domain system
#local-user admin
password cipher .]@USE=B,53Q=^Q`MAF4<1!!
service-type telnet terminal
level 3
service-type ftp
#interface Aux0
async mode flow
#interface Ethernet0/0
ip address 74.40.88.254 255.255.255.0
#interface Serial0/0
clock DTECLK1
link-protocol ppp
ip address dhcp-alloc
#interface Serial2/0
clock DTECLK1
link-protocol ppp
#interface Serial3/0
clock DTECLK1
link-protocol ppp
#interface NULL0
#info-center synchronous
#FTP server enable
#ip route-static 74.40.88.0 255.255.255.240 74.40.88.253 preference 60
#user-interface con 0
idle-timeout 0 0
user-interface aux 0
user-interface vty 0 4
authentication-mode scheme ?
#return |
路由器B：
#sysname AR2810-B
#cpu-usage cycle 1min
#router id 2.2.2.2
#radius scheme system
#domain system
#local-user admin
password cipher .]@USE=B,53Q=^Q`MAF4<1!!
service-type telnet terminal
level 3
service-type ftp
#interface Aux0
async mode flow
#interface Ethernet0/0
ip address 74.40.88.253 255.255.255.0
arp-proxy enable
#interface Serial0/0 ?
link-protocol ppp
ip address 192.168.1.1 255.255.255.252
#interface NULL0
#info-center synchronous
#FTP server enable
#ip route-static 74.40.88.0 255.255.255.240 192.168.1.2 preference 60
#user-interface con 0
idle-timeout 0 0
user-interface aux 0
user-interface vty 0 4
authentication-mode scheme
#return |
路由器C：
#sysname AR1810-C
#cpu-usage cycle 1min
#router id 3.3.3.3
#radius scheme system
#domain system
#local-user admin
password cipher .]@USE=B,53Q=^Q`MAF4<1!!
service-type telnet terminal
level 3
service-type ftp
#interface Aux0
async mode flow
#interface Ethernet0/0
ip address 74.40.88.1 255.255.255.240
#interface Serial0/0
clock DTECLK1
link-protocol ppp
ip address 192.168.1.2 255.255.255.252
#interface NULL0
#info-center synchronous
#FTP server enable
#ip route-static 74.40.88.0 255.255.255.0 192.168.1.1 preference 60
#user-interface con 0
idle-timeout 0 0
user-interface aux 0
user-interface vty 0 4
authentication-mode scheme
#return |
以上配置经测试可以互通：
S2016(PC1):
[S2016]ping 74.40.88.2
PING 74.40.88.2: 56 data bytes, press CTRL+C to break
Reply from 74.40.88.2: bytes=56 Sequence=1 ttl=253 time = 91 ms
Reply from 74.40.88.2: bytes=56 Sequence=2 ttl=253 time = 103 ms
Reply from 74.40.88.2: bytes=56 Sequence=3 ttl=253 time = 86 ms
Reply from 74.40.88.2: bytes=56 Sequence=4 ttl=253 time = 91 ms
Reply from 74.40.88.2: bytes=56 Sequence=5 ttl=253 time = 93 ms
--- 74.40.88.2 ping statistics ---
5 packet(s) transmitted
5 packet(s) received
0.00% packet loss
round-trip min/avg/max = 86/92/103 ms
[S2016]
S2008(PC2):
[S2008]ping 74.40.88.200
PING 74.40.88.200: 56 data bytes, press CTRL+C to break
Reply from 74.40.88.200: bytes=56 Sequence=1 ttl=253 time = 91 ms
Reply from 74.40.88.200: bytes=56 Sequence=2 ttl=253 time = 94 ms
Reply from 74.40.88.200: bytes=56 Sequence=3 ttl=253 time = 87 ms
Reply from 74.40.88.200: bytes=56 Sequence=4 ttl=253 time = 90 ms
Reply from 74.40.88.200: bytes=56 Sequence=5 ttl=253 time = 94 ms
--- 74.40.88.200 ping statistics ---
5 packet(s) transmitted
5 packet(s) received
0.00% packet loss
round-trip min/avg/max = 87/91/94 ms
[S2008] |