RE: Simple NAT Issue

From: Joe Astorino (joe_astorino@comcast.net)
Date: Wed Feb 04 2009 - 04:26:47 ARST


Thanks for the solution Pavel. Do you know if it is indeed true that a
router doing the NATing will not actually NAT packets that it generates,
even if the source address is in the NAT translation list? I seem to
remember this sort of thing working on older versions of IOS.
 

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  _____

From: Pavel Bykov [mailto:slidersv@gmail.com]
Sent: Wednesday, February 04, 2009 1:22 AM
To: joe_astorino@comcast.net
Cc: ccielab@groupstudy.com
Subject: Re: Simple NAT Issue

One of the solutions how to accomplish your goal is to use PBR and local
policy.
e.g.:

route-map NAT
set interface lo55
!
ip local policy route-map NAT

On Wed, Feb 4, 2009 at 6:32 AM, <joe_astorino@comcast.net> wrote:

I am having a problem regarding NAT and was hoping somebody could help me
understand this. I have a router, R5 that I wish to do NAT translation so
that anything sourced from its Loopback55 address will be translated to its
Loopback1 interface. This way I can meet a requirement that I should be able
to source a ping from Loopback55 and have it reply successfully without
adding Loopback55 to any routing protocol.

If I set this up the way I have below, and try a ping sourced from Lo55 it
does not work...no translation occurs. I thought I remember hearing
something at one point that the router doing the NAT translation won't NAT
packets sourced from itself, only packets that pass through it, but I am not
sure on that. Any ideas guys?

Just to be sure, I have checked that I do have reachability to the address I
am trying to ping when sourced from lo1.

R5(config)#do sh ip int brie | i Loop
Loopback1 99.99.99.5 YES manual up up
Loopback55 55.55.55.55 YES manual up up

R5(config)#do sh access-list 55
Standard IP access list 55
10 permit 55.55.55.55

R5(config)#do sh run int e0/0 | i ip nat
ip nat outside

R5(config)#do sh run int s2/0 | i ip nat
ip nat outside

R5(config)#do sh run int s2/0.56| i ip nat
ip nat outside

R5(config)#do sh run int s2/1 | i ip nat
ip nat outside

R5(config)#do sh run int lo1 | i nat
ip nat outside

R5(config)#do sh run int lo55 | i nat
ip nat inside

ip nat inside source list 55 interface lo1 overload

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