[p2p-hackers] UDP ports in the dynamic range

[Adam Fisk]

The only thing that comes to mind here is that some apps like RealPlayer 
and likely Windows Media Player and Quicktime select UDP ports from 
fairly broad ranges, at least the last time I checked.  I don't remember 
what those ranges were, but it's quite likely they're choosing a subset 
of the dynamic range as well, so you might just want to take a second to 
check for an overlap.  It's probably fine and not really something to 
worry about -- just putting it on your radar.

-Adam


David Barrett wrote:

> From range of ports should I randomly pick a UDP port mapping?
>
> The IANA states "The Dynamic and/or Private Ports are those from 49152 
> through 65535".  Thus I'm considering just randomly selecting from 
> within this range.
>
> However, I'm curious if you have any experience with this and and 
> either encourage or dissuade me along this path?  I personally don't 
> care which port I use, so long as I don't stumble into some "known" 
> minefield.  Do firewalls often block this range?  Do NATs do anything 
> funky with this range?  Is there any reason to use one UDP port over 
> another?  Should I secretly use on of the registered ranges to improve 
> my NAT/firewall penetration odds?
>
> An alternate plan is to choose an unregistered range from the big IANA 
> list (http://www.iana.org/assignments/port-numbers) but if there's no 
> reason not to, I'd just as soon stick with the big unregistered 
> dynamic range.
>
> Any suggestions?
>
> And finally, I'm going to try to configure a UPnP port-mapping using 
> this randomly-selected port as my external NAT port.  Does this change 
> your recommendations at all?
>
> -david
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