IPv6 woes - RFC

Thu Sep 23 19:48:09 UTC 2021

On Thu, Sep 23, 2021 at 3:42 AM Baldur Norddahl <baldur.norddahl at gmail.com>
wrote:

>
>
> tor. 23. sep. 2021 01.39 skrev Colton Conor <colton.conor at gmail.com>:
>
>> Where does this "You can only have about 200-300 subscribers per IPv4
>> address on a CGN." limit come from? I have seen several apartment
>> complexes run on a single static IPv4 address using a Mikrotik with
>> NAT.
>>
>
> It is our observation as the limit before you regularly run out of ports
> using Linux as a CGN server.
>
> It will still work if you have more users on an IP. The users will just
> experience session failures at peak. Low levels of that might show up as
> pictures that fail to load on a web page and be ok when the user reloads.
> This will increase the number of support calls and the number of customers
> that asks to escape the CGN. Or people will live with it and just think
> that the Internet connection is low quality.
>
>
This sounds like very naive nat state management behavior.
Ideally, you'd  be able to maintain state of:
original-src/dst/ports/proto -> in-interface/external ip/port/proto

unless some internal/original src is double using port/proto ... you should
really
have the ability to nat quite a large number of things to a single ipv4
address.

Of course as layers of nat get deeper you may lose some useful state :(
you may be able to use tcp seq numbers or other items in the state though
to overcome.
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