Controlling ports used by natd

Mike Silbersack silby at silby.com
Mon Dec 22 16:33:36 PST 2003


On Fri, 12 Dec 2003, Brett Glass wrote:

> net.inet.ip.portrange.lowfirst: 1023
> net.inet.ip.portrange.lowlast: 600
> net.inet.ip.portrange.first: 1024
> net.inet.ip.portrange.last: 5000
> net.inet.ip.portrange.hifirst: 49152
> net.inet.ip.portrange.hilast: 65535
>
> Why is "lowfirst" greater than "lowlast" above?

That's just an implementation issue, nothing major.  The port choosing
algorithm can handle both the cases where first > last and last > first,
and someone put the low ports in that order.

> It is also interesting that natd doesn't respect the
> "hifirst..hilast" settings here. Shouldn't it look at
> these variables and avoid assigning ports that the
> machine on which it's running would not use? Or should
> there be a "net.inet.alias.portrange.first", etc., so
> that one could specify the ranges or lists for everything
> in one place?

The high range is really a "feature" added for ftpd's sake, if you take a
look back through the cvs history.  There's no problem with the normal and
high ranges overlapping; -current uses 49152-65535 for both.

Mike "Silby" Silbersack


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