如图所示：
在61.128.64.0（PC3、4所在网段）这个网段上只允许主机61.128.64.10访问网段2，网段3：172.16.0.0（PC1所在网段）可以访问网段2，其它任何主机对网段2的访问均被拒绝。
R1的配置：
Press Enter to Start
Router>
Router>en
Router#conf t
Enter configuration commands, one per line. End with CNTL/Z.
Router(config)#host R1
R1(config)#int f0/0
R1(config-if)#ip add 172.16.0.1 255.255.255.0
R1(config-if)#no shut
%LINK-3-UPDOWN: Interface FastEthernet0/0, changed state to up
R1(config-if)#int f0/1
R1(config-if)#ip add 192.168.1.1 255.255.255.0
R1(config-if)#no shut
%LINK-3-UPDOWN: Interface FastEthernet0/1, changed state to up
R1(config-if)#end
R1#conf t
Enter configuration commands, one per line. End with CNTL/Z.
R1(config)#int s0
R1(config-if)#ip add 172.16.1.1 255.255.255.0
R1(config-if)#no shut
%LINK-3-UPDOWN: Interface Serial0, changed state to up
R1(config-if)#
R1(config-if)#exit
R1(config)#router rip
R1(config-router)#version 2
R1(config-router)#network 172.16.0.0
R1(config-router)#network 192.168.1.0
R1(config-router)#network 172.16.1.0
R1(config-router)#end
R1#conf t
Enter configuration commands, one per line. End with CNTL/Z.
R1(config)#access-list 1 permit 61.128.64.10 0.0.0 .0
R1(config)#access-list 1 permit 172.16.0.0 0.0.0 .255
R1(config)#int f0/1
R1(config-if)#ip access-group 1 out
R1(config-if)#end
R2的配置：
Router#conf t
Enter configuration commands, one per line. End with CNTL/Z.
Router(config)#host R2
R2(config)#int f0/0
R2(config-if)#ip add 61.128.64.1 255.255.255.0
R2(config-if)#no shut
%LINK-3-UPDOWN: Interface FastEthernet0/0, changed state to up
R2(config-if)#int s0
R2(config-if)#ip add 172.16.1.2 255.255.255.0
R2(config-if)#clock rate 64000
R2(config-if)#no shut
%LINK-3-UPDOWN: Interface Serial0, changed state to up
%LINK-3-UPDOWN: Interface Serial0, changed state to down
%LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0, changed state to down
%LINK-3-UPDOWN: Interface Serial0, changed state to up
%LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0, changed state to up
R2(config-if)#exit
R2(config)#router rip
R2(config-router)#version 2
R2(config-router)#network 172.16.1.0
R2(config-router)#network 61.128.64.0
R2(config-router)#end
PC的IP参数配置：
PC1：172.16.0.2/24 172.16.0.1
PC2：192.168.1.2/24 192.168.1.1
PC3：61.128.64.10/24 61.128.64.1
PC4：61.128.64.20/24 61.128.64.1
配置好之后再检验一下就OK。
