Cisco IOS Cookbook, 2nd Edition

Translating Some Addresses Statically and Others Dynamically

Problem

You want certain hosts to have static address translation properties and all others to use dynamic translation.

Solution

In some cases you might need to use a combination of the two approaches. Some internal devices will always translate to specific external addresses, but others will use a dynamic pool. This is often the case when you have a few internal servers that need to be accessed from outside of the network, but other devices that will only make outbound connections:

Router#configure terminal
Enter configuration commands, one per line.  End with CNTL/Z.
Router(config)#access-list 15 deny 192.168.1.15 0.0.0.0
Router(config)#access-list 15 deny 192.168.1.16 0.0.0.0
Router(config)#access-list 15 permit 192.168.0.0 0.0.255.255
Router(config)#ip nat inside source static 192.168.1.15 172.16.1.10
Router(config)#ip nat inside source static 192.168.1.16 172.16.1.11
Router(config)#ip nat pool NATPOOL 172.16.1.100 172.16.1.150 netmask 255.255.255.0
Router(config)#ip nat inside source list 15 pool NATPOOL overload
Router(config)#interface FastEthernet0/0
Router(config-if)#ip address 192.168.1.1 255.255.255.0
Router(config-if)#ip nat inside
Router(config-if)#exit
Router(config)#interface FastEthernet0/1
Router(config-if)#ip address 192.168.2.1 255.255.255.0
Router(config-if)#ip nat inside
Router(config-if)#exit
Router(config)#interface Ethernet0/0
Router(config-if)#ip address 172.16.1.2 255.255.255.0
Router(config-if)#