We are looking for a clarification of ASA nat-control command. Unfortunately, we don't have spare device to test it out.
The situation is as follows:
An ASA firewall has three interfaces: "inside", "outside", and "corpinside".
nat-control is DISABLED.
A GLOBAL statment is defined on the "outside" interface and the correpsonding NAT statement on the "inside" interface, something like:
global(outside) 1 ...
nat (inside) 1 ...
We confirmed packets from "inside" to "outside" are allowed even for the packes that do not match any NAT rules (including Static NAT, DynamicNAT, and NAT Exempt).
The issue is what happens to traffice from "inside" to "corpinside" if no Dynamic NAT is defined from "inside" to "corpinside" and two interfaces have
different secuity levels.
One interpretation is: Since NAT is disabled, all traffic from "inside" to "corpinside" should be allowed.
Another interpretation: If dynamic NAT is configured on an interface, all traffic from that interface to any other interface must hit a NAT rule, therefore traffic from "inside" to "corpinside" should be denied .
We need a clarification of which interpretation is correct.
Also,if "inside" and "corpinside" are at the same security level, then is the traffic allowed?
Even with NAT control disabled, you need to perform NAT on any addresses for which you configure dynamic NAT. When NAT control is disabled, and a NAT and a global command pair are configured for an interface, the real IP addresses cannot go out on other interfaces unless you define those destinations with the nat 0 access-list command.
Table of ContentsIntroductionVersion HistoryPossible Future
UpdatesDocuments PurposeNAT Operation in ASA 8.3+ SectionsRule Types
Network Object NATTwice NAT / Manual NATRule Types used per SectionNAT
Types used with Twice NAT / Manual NAT and Network Obje...
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