Re: Using outside DNS name to access internal server from inside the network


<scooty@xxxxxxxxxxxxx> wrote in message
news:1142749143.327120.75460@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Hi all
A strange request from a client which I am unsure can be achived using
NAT
The client has a mail server, say 172.16.50.20 and it's DNS name for
example is mail.test.com.au to the outside world
mail.test.com.au also maps to a real IP address as one would expect,
which is the IP address of the WAN interface on the Cisco router. The
client wants to be able to access mail.test.com.au using the external
DNS reference on say port 8081 (internally)
So any user who opens a browser inside the private network, points it
to mail.test.com.au:8081 should be able to access the mail server.
mail.test.com.au is located inside the network but is using the outside
IP address as dNS resolution is giving the inside user a real IP for
mail.test.com.au.
My question is can this be achieved? I hope I have explained myself
well enough for this to make sense!


This can be done if the gateway is just a router. Using either external or
internal DNS, if this resolves to the global IP address then some devices
allow traffic to be sent to the gateway with a destination of the live IP
address, NATed and then sent back into the network. Some devices such as the
Cisco Pix do not allow this as with the Pix any traffic entering one network
interface has to exit from a different interface. You can't NAT "on a stick"
so to speak.

I *think* that with a router this might be okay. However, the best option is
always internal DNS and "views".

Chris.


.

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