Re: NAT on a Trident/Qumran(/or other?) equipped whitebox?

[James Bensley <jwbensley () gmail com>]

On Mon, 15 Oct 2018 at 10:07, <adamv0025 () netconsultings com> wrote:
> Interesting, but isn’t stateful tracking once again just swapping, but in this case port 123 in port 32123 out?
>
> So none of the chips you named below support swapping parts of L4 header and that part is actually done with SW 
> assistance please?
>
> So for example the following:
>
> https://eos.arista.com/7150s-nat-practical-guide-source-nat-dynamic/#2Dynamic_Source_NATOverload_Many_to_one
>
> - wouldn’t be at line-rate please?

Hi Adam,

NAT/PAT is an N:1 swapping (map) though so a state/translation table
is required to correctly "swap" back the return traffic. MPLS for
example is 1:1 mapping/action. NAT/PAT state tables tend to fill
quickly so to aid with this we also have timers to time out the
translations and free up space in the translation table, and also
track e.g. TCP RST or TCP FIN to remove entries from the table, so
it's not "just swapping".

Cheers,
James.