Cisco Routers, NAT and DNS...

[Lordy]

Hi Roy,

I'm sorry but I don't know exactly where to find that in the Cisco Docs. I just
remember that one of our customers had a problem with that and he mailed
me an excerpt from the Cisco Page that I couldn't find anymore unfortunately.

However, just to summarize it:

Let's say you have a public network 1.2.3.0/24 natting to 192.168.1.0/24.
When you query an external nameserver for a host that points to 1.2.3.X
the Cisco will "catch" the response packet and exchange 1.2.3.X with
192.168.1.X.

That can lead to some real confusion. Our customer thought had we had bad
data in our NS but as I checked we had the real IP adresses. It took me a while
to figure out that it was the Cisco doing this.

I hope I explained it in a way, so everybody understands.

Regards,
Lordy

P.S: If I find some documents on that I'll post them to the list later.


At 00:11 23.06.2001 +0200, you wrote:
>On Fri, 22 Jun 2001, Lordy wrote:
>
> > Hi Michael,
> >
> > i have seen this before and it's documented in the Cisco Docs. As I'm not
> > a Cisco expert I don't know if you can turn off that feature but as far 
> as I
> > have looked at it I could find any way to do that.
> >
> > The only workaround is probably to give your dns-server a public 
> routeable IP.
> >
> > Regards,
> > Lordy
>
>Do you have a pointer wrt to this problem ? You mentioned it is documented
>in the Cisco Docs. I'm really interested to read up on that.
>
>Regards,
>
>Roy Arends
>Nominum