Re: maximum ipv4 bgp prefix length of /24 ?

[Owen DeLong via NANOG <nanog () nanog org>]

> On Sep 28, 2023, at 23:57, Vasilenko Eduard <vasilenko.eduard () huawei com> wrote:
>
> Well, it depends.
> The question below was evidently related to business.
> IPv6 does not have yet a normal way of multihoming for PA prefixes.

The normal way for IETF (which is, IMHO, borked to put it mildly) is to use multiple
prefixes and leave source address selection as an exercise for the victim^wend
user.

The obviously better approach is for anyone who cares about such a thing to get
a /48 and an ASN from their friendly neighborhood RIR and move on.

> If IETF (and some OTTs) would win blocking NAT66,

This is an expansion of the problem, not a solution.

> Then /48 propoisiton is the proposition for PA (to support multihoming).

If you’re using a /48, why use PA?

> Unfortunately, it is at least a 10M global routing table as it has been shown by Brian Carpenter.

Not right away and this is an eventuality we will need to face sooner or later anyway.

> Reminder, The IPv6 scale on all routers is 2x smaller (if people would use DHCP and longer than/64 then the scale 
> would drop 2x additionally).

Which remains a bad idea for so many other reasons in addition to this one.

> Hence, /48 proposition may become 20x worse for scale than proposed initially in this thread.

I don’t see it that way.

Routing tables are going to continue to grow regardless of what we do in terms of end site addressing.
Router vendors will build what is needed. The ability to handle a 10M route table is known technology at
this point, and its just a matter of the cost of the line cards.

Owen

> Eduard
> From: NANOG [mailto:nanog-bounces+vasilenko.eduard=huawei.com () nanog org] On Behalf Of Owen DeLong via NANOG
> Sent: Friday, September 29, 2023 7:11 AM
> To: VOLKAN SALİH <volkan.salih.06 () gmail com>
> Cc: nanog () nanog org
> Subject: Re: maximum ipv4 bgp prefix length of /24 ?
>  
> Wouldn’t /48s be a better solution to this need?
>  
> Owen
>  
>
>
> On Sep 28, 2023, at 14:25, VOLKAN SALİH <volkan.salih.06 () gmail com <mailto:volkan.salih.06 () gmail com>> wrote:
>  
> hello,
>
> I believe, ISPs should also allow ipv4 prefixes with length between /25-/27 instead of limiting maximum length to 
> /24..
>
> I also believe that RIRs and LIRs should allocate /27s which has 32 IPv4 address. considering IPv4 world is now 
> mostly NAT'ed, 32 IPv4s are sufficient for most of the small and medium sized organizations and also home office 
> workers like youtubers, and professional gamers and webmasters!
>
> It is because BGP research and experiment networks can not get /24 due to high IPv4 prices, but they have to get an 
> IPv4 prefix to learn BGP in IPv4 world.
>
> What do you think about this?
>
> What could be done here?
>
> Is it unacceptable; considering most big networks that do full-table-routing also use multi-core routers with lots of 
> RAM? those would probably handle /27s and while small networks mostly use default routing, it should be reasonable to 
> allow /25-/27?
>
> Thanks for reading, regards..