[nsp] Really strange NAT Problem

Mark Tinka mtinka at africaonline.co.sz
Thu Feb 26 01:45:25 EST 2004

cisco-nsp-bounces at puck.nether.net wrote:
> I'm declaring the loopback interface as "ip nat outside" because
> that's the address I'm trying to NAT to. I've got two interfaces that
> lead back into our network: FastEthernet0/0 and Serial0/0. These
> interfaces run some routing protocols so that if one were to go down,
> traffic would fail over to the other. These two interfaces are
> declared as "ip nat outside" as well.     

I am guessing your s0/0 interface provides your WAN connectivity. Since you
have an IP address on your loopback interface, and you seem to want it that
way, why don't you unnumber your s0/0 interface onto your loopback
interface, making your s0/0 interface 'ip nat outside', and then overloading
your NAT statement onto the loopback interface?

What this accomplishes is that your router knows that s0/0 is your 'ip nat
outside' interface, but it knows to use the IP address of the loopback
interface as its source. 

I hope this makes sense. I do it all the time :).


Mark Tinka
Technical Manager, Africa Online Swaziland

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