一、实验配置图

1、设置三层交换机sw

sw#conf t 
Enter configuration commands, one per line.  End with CNTL/Z.
sw(config)#no ip routing 
sw(config)#

2、设置路由R1

R1#conf t 
Enter configuration commands, one per line.  End with CNTL/Z.
R1(config)#int f 0/1
R1(config-if)#ip add 192.168.20.1 255.255.255.0         //仅设置IP地址与子网掩码
R1(config-if)#no shut 
*Mar  1 00:00:54.063: %LINK-3-UPDOWN: Interface FastEthernet0/1, changed state to up
*Mar  1 00:00:55.063: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/1, changed state to up
R1(config-if)#int f 0/0
R1(config-if)#ip add 192.168.100.1 255.255.255.0          //仅设置IP地址与子网掩码
R1(config-if)#no shut 
R1(config-if)#ex 
*Mar  1 00:01:08.423: %LINK-3-UPDOWN: Interface FastEthernet0/0, changed state to up
*Mar  1 00:01:09.423: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/0, changed state to up
R1(config)#

3、对三台PC机进行设置

PC1
PC1> 
PC1> ip 192.168.20.20 192.168.20.1
Checking for duplicate address...
PC1 : 192.168.20.20 255.255.255.0 gateway 192.168.20.1

PC1>
PC2
PC2> 
PC2> ip 192.168.20.30 192.168.20.1 
Checking for duplicate address...
PC1 : 192.168.20.30 255.255.255.0 gateway 192.168.20.1

PC2> 
PC3
PC3> 
PC3> ip 192.168.100.10 192.168.100.1
Checking for duplicate address...
PC1 : 192.168.100.10 255.255.255.0 gateway 192.168.100.1

注意：此时理论上是已经可以做到全网互通的。。

4、在R1上配置动态NAT列表

R1(config)#
R1(config)#ip  access-list  standard   kgc                          //设置命名访问控制列表
R1(config-std-nacl)#permit  192.168.20.0  0.0.0.255 
R1(config)#ip  nat  pool  test 12.0.0.10 12.0.0.20  netmask  255.255.255.0     //设置公网地址池
R1(config)#
*Mar  1 00:09:46.123: %LINEPROTO-5-UPDOWN: Line protocol on Interface NVI0, changed state to up
R1(config)#ip  nat  inside  source  list  kgc  pool  test                  //实现网络地址转换

R1(config)#int  f0/1
R1(config-if)#ip  nat  inside                          //启用内部NAT
R1(config-if)#int  f0/0
R1(config-if)#ip  nat  outside                         //启用外部NAT
R1(config-if)#ex 

验证结果

以上就是动态NAT的地址转换，不需要手动进行指定转换地址，能自动转换区间范围内的地址