From: Don Dettmore (don@xxxxxxxxxxxxx)
Date: Fri Jun 08 2001 - 12:37:34 GMT-3
I'm trying to understand how NAT works a little better - maybe someone can
explain this to me.
The following refers to a two-way NAT scenario - that is, where both the
source and destination addresses are translated.
I've noticed that when a packet comes in an 'inside' interface (destined for
an outside interface), first the route lookup occurs, and THEN it is
translated. But when a packet comes in an 'outside' interface (destined for
an inside interface) first it is translated, THEN the route lookup occurs.
Why the difference. A beneficial side effect is that your routing table need
only be composed of inside routes. Is that the reason?
I've only implemented this in situations where I had but one outside
interface. Does this have anything to do with the results I'm seeing? It
would seem to me that if there were more than one outside interface, the NAT
could not occur first - as possible no NAT need occur (I guess there's
something to try in the lab).
Anyone have any ideas?
TIA
Don Dettmore
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