nanog mailing list archives

Re: IPv6 woes - RFC


From: Colton Conor <colton.conor () gmail com>
Date: Thu, 23 Sep 2021 10:34:16 -0500

300 apartments Mark. No, it's bulk internet and wifi so a single provider.

On Wed, Sep 22, 2021 at 8:01 PM Mark Andrews <marka () isc org> wrote:

And how many apartments where covered by that single IP address? Was this
where there is a restriction on other providers so the occupants had no
choice of wireline ISP?

On 23 Sep 2021, at 09:38, Colton Conor <colton.conor () gmail com> wrote:

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.

On Wed, Sep 22, 2021 at 2:49 PM Baldur Norddahl
<baldur.norddahl () gmail com> wrote:



On Wed, 22 Sept 2021 at 16:48, Masataka Ohta <mohta () necom830 hpcl titech ac jp> wrote:

Today, as /24 can afford hundreds of thousands of subscribers
by NAT, only very large retail ISPs need more than one
announcement for IPv4.


You can only have about 200-300 subscribers per IPv4 address on a CGN. If you try to go further than that, for 
example by using symmetric NAT, you will increase the number of customers that want to get a public IPv4 of their 
own. That will actually decrease the combined efficiency and cause you to need more, not less, IPv4 addresses.

Without checking our numbers, I believe we have at least 10% of the customers that are paying for a public IPv4 to 
escape our CGN. This means a /24 will only be enough for about 2500 customers maximum. The "nat escapers" drown 
out the efficiency of the NAT pool.

The optimization you need to do is to make the CGN as customer friendly as possible instead of trying to squeeze 
the maximum customers per CGN IPv4 address.

Perhaps IPv6 can lower the number of people that need to escape IPv4 nat. If it helps just a little bit, that 
alone will make implementing IPv6 worth it for smaller emerging operators. Buying IPv4 has become very expensive. 
Yes you can profit from selling a public IPv4 address to the customer, but there is also the risk that the 
customer just goes to the incumbent, which has old large pools of IPv4 and provides it for free.

Regards,

Baldur


--
Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742              INTERNET: marka () isc org



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