From: Florian Westphal <fw@strlen.de>
To: Daniel <tech@tootai.net>
Cc: netfilter@vger.kernel.org
Subject: Re: NAT - how external source port is selected
Date: Wed, 18 Aug 2021 16:46:15 +0200 [thread overview]
Message-ID: <20210818144615.GQ607@breakpoint.cc> (raw)
In-Reply-To: <9cc05668-b4fb-4ed8-1588-7a0f5c378b3a@tootai.net>
Daniel <tech@tootai.net> wrote:
> how on a NAT firewall server using iptables or nftables, are the external
> source ports choosen ? I would say range is 1024-65535 but if for instance I
> use port 5060 for SIP this one can not be used as source port. Is there a
> table of at time used ports ?
Are you talking about SNAT/MASQUERADE?
It will try to use whatever port is used. If the source address
replacement results in a collision, it tries to pick a different source
port between 1024 and 65535.
> Also, SNOM phones are systematically using port 2048 as source port of the
> WAN ip. Is there a mechanism to allow such behavior ?
What do you mean? The initiator is free to pick whatever source port they like.
next prev parent reply other threads:[~2021-08-18 14:46 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-18 13:53 NAT - how external source port is selected Daniel
2021-08-18 14:22 ` Reindl Harald
2021-08-18 14:50 ` Daniel
2021-08-18 15:15 ` Reindl Harald
2021-08-18 14:46 ` Florian Westphal [this message]
2021-08-18 15:12 ` Daniel
[not found] ` <20210818161622.GS607@breakpoint.cc>
2021-08-18 16:43 ` Daniel
2021-08-18 14:52 ` AW: " Thomas Bätzler
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