Re: [Ntp] NAT devices not translating privileged ports

Hal Murray <halmurray+ietf@sonic.net> Fri, 04 June 2021 08:07 UTC

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To: Fernando Gont <fernando.gont@edgeuno.com>
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From: Hal Murray <halmurray+ietf@sonic.net>
In-Reply-To: Message from Fernando Gont <fernando.gont@edgeuno.com> of "Fri, 04 Jun 2021 07:02:29 -0000." <c576bad79151f48543179594b4ea2bc46c85cdb6.camel@edgeuno.com>
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Date: Fri, 04 Jun 2021 01:07:16 -0700
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Subject: Re: [Ntp] NAT devices not translating privileged ports
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fernando.gont@edgeuno.com said:
> we were asked if we could provide a reference for the NAT devices do not
> translate the source port if the source port is a privileged port (<1024).

> Any clues/examples of this type of NATs?

Does that make sense?  What happens if 3 systems inside the NAT box all send 
using the same privileged source port?  ntpd without port randomization would 
do that.

There is the special case where you want to run a server (on a privileged 
port) located inside the NAT box.  I think Port forwarding is the usual term.  
In that case, you have to tell the NAT box the (internal) IP Address of the 
server.  Some/most implementations allow you to change the port number.

-- 
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