Source and Destination NAT


Can you explain Source and Destination Nat in ASA and also in IOS with a scenario… Please…

Hi Sushanth,

Source NAT is typically used for Internet access where we translate the source address of a host to the public IP address of our router. Here is an example for Cisco IOS and ASA:

Destination NAT is typically used for load balancing. We translate the destination when the packet goes from the outside to the inside. I don’t have a complete lesson for this but here is a quick example for Cisco IOS. Here’s the config of the NAT router:

hostname R1
ip cef
interface GigabitEthernet0/1
 ip address
 ip nat inside
interface GigabitEthernet0/2
 ip address
 ip nat outside
ip nat pool TELNET_SERVERS prefix-length 24 type rotary
ip nat inside destination list PUBLIC_IP pool TELNET_SERVERS
ip access-list standard PUBLIC_IP

We have two telnet servers, and This router can use on the outside, this could be a public IP.

When a device on the outside ( connects to, the first time you get:

NAT*: s=, d=> [47462]

And the second time:

NAT*: s=, d=> [11370]

So it gets load balanced to first, then to

Hope this is helpful!


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