Allocating External Addresses Statically
Problem
You want to translate specific internal IP addresses to specific external addresses.
Solution
For some applications, you need each internal (inside local) address to always translate to the same external (inside global) address. This is particularly true if you need inbound connections from the outside network to always reach a particular internal device, such as a web or email server:
Router#configure terminal
Enter configuration commands, one per line. End with CNTL/Z. Router(config)#ip nat inside source static
Router(config)#
192.168.1.15 172.16.1.10
ip nat inside source static
Router(config)#
192.168.1.16 172.16.1.11
interface
Router(config-if)#
FastEthernet 0/0
ip address
Router(config-if)#
192.168.1.1 255.255.255.0
ip nat inside
Router(config-if)#exit
Router(config)#interface
Router(config-if)#
FastEthernet 0/1
ip address
Router(config-if)#
192.168.2.1 255.255.255.0
ip nat inside
Router(config-if)#exit
Router(config)#interface
Router(config-if)#
Ethernet1/0
ip address
Router(config-if)#
172.16.1.2 255.255.255.0
ip nat outside
Router(config-if)#exit
Router(config)#end
Router#
Discussion
This recipe includes static translations for two internal
devices. The internal address 192.168.1.15
will always appear on the
outside as 172.16.1.10
, and
192.168.1.16
will always appear as
172.16.1.11
. Note that because these translations are static, they will work in either direction. So any packets sent to the NAT address from the external network will reach ...
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