From: joe_astorino@comcast.net
Date: Wed Feb 04 2009 - 03:32:05 ARST
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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