[p2p-hackers] Unidirectional or Bidirectional Manual Port Forwarding?

[coderman]

On 8/17/05, David Barrett <dbarrett at quinthar.com> wrote:
> 1) Are manually-forwarded NAT port mappings typically unidirectional or
> bidirectional?  Does this depend on the NAT model?

This is NAT specific behavior / implementation dependant.  What you
describe is not uncommon, since UDP is stateless many NAT's lazily
assume that port forwards operate in one direction.


> 2) Is it possible to manually configure the outbound mapping (ie, force
> all traffic originating from an internal endpoint to use a specific
> external endpoint)?

You can do this with Linux NAT's and probably others, but I doubt
D-Link will be cooperative.  Just to verify, the internal IP:port is
using the same port as the one configured in the nat to forward
traffic to, correct?


> 2) What type of mapping does UPnP attempt to establish?

UPnP tends to make a mapping more in line with that you except.  That
is to say, if UDP traffic exits from an internal IP:Port that matches
a UPnP static mapping rule, it will exit from the public endpoint
defined in the mapping.  I believe I tried this with a Linksys router
and it worked ok; I have no idea about D-Link.

You may want to dig around on some game sites about UDP port forwards
with the D-Link device you are using.  There are some multi-player
games which rely on loose UDP NAT or port forwards and they may have
some insight into the particular problem you are experiencing.