问题
在R1通过动态NAT实现企业内网192.168.1.0/24转换为公网地址61.159.62.131-61.159.62.134，访问192.168.2.1
方案
步骤
动态NAT配置
删除配置端口映射中的端口映射
tarena-R1 (config)#noip nat inside source static tcp 192.168.1.3 80 61.159.62.133 80
在R1上配置ACL
tarena-R1(config)#access-list1 permit 192.168.1.0 0.0.0.255
在R1上配置可转换的公网IP地址池
地址池是向ISP（Internet服务提供商，如电信、联通,移动）申请得到的，内网主机（上一步ACL中所包含的IP地址）到外网的访问，内网地址将被动态的、随机的转换为这些合法地址。
arena-R1(config)#ipnat pool natpool 61.159.62.131 61.159.62.134 netmask 255.255.255.248
关联ACL和公网的IP地址池
tarena-R1(config)#ipnat inside source list 1 pool natpool
在R1上配置NAT内、外端口
tarena-R1(config)#interface f0/0
tarena-R1(config-if)#ip nat inside
tarena-R1(config-if)#interface f0/1
tarena-R1(config-if)#ip nat outside
分别在两台PC机上测试到外网主机的通信
PC1测试如下所示：PC>ipconfig
FastEthernet0 Connection:(default port)
Link-local IPv6 Address.........: FE80::2D0:FFFF:FE45:CACC
IP Address......................: 192.168.1.1
Subnet Mask.....................: 255.255.255.0
Default Gateway.................: 192.168.1.254
PC>ping 192.168.2.1
Pinging 192.168.2.1 with 32 bytes of data:
Reply from 192.168.2.1: bytes=32 time=1ms TTL=126
Reply from 192.168.2.1: bytes=32 time=0ms TTL=126
Reply from 192.168.2.1: bytes=32 time=0ms TTL=126
Reply from 192.168.2.1: bytes=32 time=0ms TTL=126
Ping statistics for 192.168.2.1:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 0ms, Maximum = 1ms, Average = 0ms
PC2测试如下所示：PC>ipconfig
FastEthernet0 Connection:(default port)
Link-local IPv6 Address.........: FE80::2D0:FFFF:FE45:CACC
IP Address......................: 192.168.1.2
Subnet Mask.....................: 255.255.255.0
Default Gateway.................: 192.168.1.254
PC>ping 192.168.2.1
Pinging 192.168.2.1 with 32 bytes of data:
Reply from 192.168.2.1: bytes=32 time=1ms TTL=126
Reply from 192.168.2.1: bytes=32 time=0ms TTL=126
Reply from 192.168.2.1: bytes=32 time=0ms TTL=126
Reply from 192.168.2.1: bytes=32 time=0ms TTL=126
Ping statistics for 192.168.2.1:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 0ms, Maximum = 1ms, Average = 0ms
在R1上查看NAT转换表
转换表中的对应关系是动态的，如192.168.1.1被转换为61.159.62.131，但是下一次对外网的访问很有可能被转换为其他地址。
tarena-R1#show ip nat translations
Pro Inside global Inside local Outside local Outside global
icmp 61.159.62.131:1362192.168.1.1:1362 192.168.2.1:1362 192.168.2.1:1362
icmp 61.159.62.131:1392192.168.1.1:1392 192.168.2.1:1392 192.168.2.1:1392
icmp 61.159.62.131:1393192.168.1.1:1393 192.168.2.1:1393 192.168.2.1:1393
icmp 61.159.62.131:1394192.168.1.1:1394 192.168.2.1:1394 192.168.2.1:1394
icmp 61.159.62.132:13 192.168.1.2:13 192.168.2.1:13 192.168.2.1:13
icmp 61.159.62.132:14 192.168.1.2:14 192.168.2.1:14 192.168.2.1:14
icmp 61.159.62.132:15 192.168.1.2:15 192.168.2.1:15 192.168.2.1:15
icmp 61.159.62.132:16 192.168.1.2:16 192.168.2.1:16 192.168.2.1:16