Route lookup wont work, it needs to be used in static nat.

Do you have any other nat statement configured. 

Sam


Sent from Samsung Mobile

-------- Original message --------
From: Joe Astorino <[email protected]> 
Date: 20/06/2013  07:01  (GMT+05:30) 
To: OSL Security <[email protected]> 
Subject: Re: [OSL | CCIE_Security] 8.4 VPN Hairpin 
 
Anybody? Really interested to know the answer. I have read everything I can 
find on the topic.

Sent from my iPhone

On Jun 19, 2013, at 9:42 AM, Joe Astorino <[email protected]> wrote:

So another NAT question with 8.4 code.  Say you have RA VPN configured such 
that the VPN pool is 192.168.50.0/24.  You wish to configure hairpinning so 
that VPN users can access the internet off the ASA.  

I figured hey...I need to PAT for inside --> outside, DMZ --> outside as well 
as VPN outside --> outside so why not use "any" and be super efficient!??

object network obj_any
 nat (any,outside) dynamic interface

When connected to VPN and attempting to ping an internet address this fails due 
to rpf-check on the packet-tracer output.  Packet tracer shows these steps

Phase: 8
Type: NAT
Subtype:
Result: ALLOW
Config:
object network obj_any
 nat (any,outside) dynamic interface
Additional Information:
Dynamic translate 192.168.50.50/0 to 50.198.34.193/52258

Phase: 9
Type: NAT
Subtype: rpf-check
Result: DROP
Config:
object network obj_any
 nat (any,outside) dynamic interface
Additional Information:


I suppose what this is saying is that the nat (any,outside) bit would probably 
get hit again for the return traffic, thus trying to PAT the return traffic to 
the outside interface.

If I do this it works:

object network obj_any
 nat (inside,outside) dynamic interface
!
object network obj-192.168.50.0
 nat (outside,outside) dynamic interface


I know this works, but I don't understand why the first option doesn't work.  
With the first configuration I expect:

- packet comes in from the VPN on the outside interface and will be hairpin 
routed back out the same interface

- The nat (any,outside) rule matches as the ingress interface "any" should 
match the outside
- dynamic PAT is done such that the source is translated to the outside 
interface IP
- xlate is created

- When the return traffic comes back, it should see the xlate table and 
translate things back.  

So I guess it comes down to the return traffic.  Why would the return traffic 
hit the nat (any,outside) rule and not just be unnatted going back to where it 
came from based on the xlate table.

Thanks for any help



-- 
Regards,

Joe Astorino
CCIE #24347
http://astorinonetworks.com

"He not busy being born is busy dying" - Dylan
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