[arin-announce] IPv4 Address Space (fwd)

Wed Oct 29 14:37:39 UTC 2003

Simon Lockhart wrote:
> Anything that relies on knowing which host it is talking to by
> looking at the source address of packets breaks.
Indeed. Novell networking for example - or MS Exchange New Mail
notification.  of course, you shouldn't be doing either on the internet,
but a common "small branch office" solution involves ADSL, NAT and a
single VPN client....

> Plenty of UDP based apps work over NAT.
depends a lot on the nat - if the UDP app isn't port-specific, then often
a "smart" nat can create a virtual map for it (and IPSec NAT traversal
often relies on a single internal initiator creating such a map on the nat
device, and the destination not minding too much)
If the "outside" sender expects the recipient to be on a fixed port
though, often the best you can hope for is that *one* internal host can
receive data.