cancel
Showing results for 
Search instead for 
Did you mean: 
cancel
663
Views
5
Helpful
1
Replies

Cisco IOS NAT order of operations using inside and outside interfaces

Sam Brynes
Level 1
Level 1

This Cisco article talks about the Cisco IOS order of operations:

https://www.cisco.com/c/en/us/support/docs/ip/network-address-translation-nat/6209-5.html

Under outside-to-inside, NAT is listed before routing. How does that work in practice?

I think the router will need to do a route lookup first so that the router knows what NAT operation to do (if any). The ingress interface where the router receives the packet will need to have "ip nat outside" and the next hop interface of the router will need to have "ip nat inside" configured.

If the "route lookup" function needs to happen before NAT, how is the "route lookup" function than the "routing" item?

1 Reply 1

You hit some limitation in NAT if I am right and it list in below link, the solution is config NAT with route-map to make router match source & destination in NAT since NAT will done before route-lookup 
https://www.cisco.com/c/en/us/support/docs/security/ios-network-address-translation-nat/212922-unexpected-behaviour-of-dynamic-nat-with.html

Getting Started

Find answers to your questions by entering keywords or phrases in the Search bar above. New here? Use these resources to familiarize yourself with the community: