routing behaviour (PAT/NAT)

itemprop="text">

 |(eth0:
            84.23.13.43)
 +--------------+
 | |
 | NAT router
            |

 | |
 +--------------+
 |(eth1:
            192.168.0.1)
 |
 ----------------
 ( )
 +--+ (
            )
 |__|------( 192.168.0.0/24 )
 /____\ ( )
 Host-A
            (________________)

(192.168.0.2)

/>

Assuming we have above network situation and a
destination PAT/NAT rule configured on the NAT router for eth0 which forwards all
incoming packages with destination port TCP/80 to Host-A (192.168.0.2) I have following
question:

What happens when a Host-B
(192.168.0.10) in the local networks sends a HTTP request to 84.23.13.43? Some routers
seem to manage this situation correctly others not. Is there a technical expression
describing this situation? How can I find out which router can manage such internal
request on an external ip and which not?

class="post-text" itemprop="text">

class="normal">Answer

The
technical term for this would be NAT hairpinning or NAT U-turns. Not all home routers do
this correctly, but those are off-topic here. Any router used in a professional
environment would let you set this up
properly.

Another way to "solve" this
problem is split DNS views, where internally hostnames would resolve to the internal IP
addresses instead of the external ones. In a more complex network I would be in favor of
that, but for what you sketch above, NAT hairpinning is easier.