nanog mailing list archives
Re: maximum ipv4 bgp prefix length of /24 ?
From: Owen DeLong via NANOG <nanog () nanog org>
Date: Thu, 5 Oct 2023 12:11:11 -0700
I think it needs to be slightly more nuanced than that… Because IPv4 is driven to dense-packing and tight allocations, I think disaggregation of IPv4 will only increase over time. The hope is that by issuing larger than needed blocks of IPv6, less disaggregation becomes necessary over time. So far, that seems to be largely the case, with more than 50% of ASNs represented in the DFZ in IPv6, we see roughly 191884 unique destinations in IPv6 and 942750 unique destinations in IPv4 (admittedly an instantaneous snapshot a few moments ago from a single DFZ router, YMMV). Even if we double the IPv6 prefix count or even quadruple it, we’re still looking at a much smaller level of disaggregation in IPv6 than IPv4 in the current state. Owen
On Oct 4, 2023, at 22:49, Crist Clark <cjc+nanog () pumpky net> wrote: Been resisting adding to this thread... But if the assumption is that networks will always eventually totally deaggregate to the maximum, we're screwed. Routing IPv4 /32s would be nothing. The current practice of accepting /48s could swell to about 2^(48 - 3) = 2^45 = 35184372088832. What will prevent unrestricted growth of the IPv6 table if operators push everything out to /48 "to counter hijacks" or other misguided reasons? On Wed, Oct 4, 2023 at 8:14 AM Owen DeLong via NANOG <nanog () nanog org <mailto:nanog () nanog org>> wrote:If you maximally disaggregate to /24, you end up with about 12M fib entries. At /25 this doubles and you double it again for every bit you move right. At /24, we are on borrowed time without walking right. Also, the CPU in most routers won’t handle the churn of a 10M prefix RIB. OwenOn Oct 4, 2023, at 03:15, Mark Tinka <mark@tinka.africa> wrote: On 10/4/23 12:11, Musa Stephen Honlue wrote: Which one is easier, 1. Convincing the tens of thousands of network operators and equipment vendors to modify configs and code to accept more specifics than /24, orEquipment vendors can already support 10 million entries in FIB. They just ask for a little bit of cash for it. Mark.
Current thread:
- Re: maximum ipv4 bgp prefix length of /24 ?, (continued)
- Re: maximum ipv4 bgp prefix length of /24 ? William Herrin (Oct 04)
- Re: maximum ipv4 bgp prefix length of /24 ? Musa Stephen Honlue (Oct 04)
- Re: maximum ipv4 bgp prefix length of /24 ? Mark Tinka (Oct 04)
- Re: maximum ipv4 bgp prefix length of /24 ? Owen DeLong via NANOG (Oct 04)
- Re: maximum ipv4 bgp prefix length of /24 ? Crist Clark (Oct 04)
- Re: maximum ipv4 bgp prefix length of /24 ? Mark Tinka (Oct 04)
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- Re: maximum ipv4 bgp prefix length of /24 ? Mark Tinka (Oct 04)
- Re: maximum ipv4 bgp prefix length of /24 ? Owen DeLong via NANOG (Oct 05)
- Re: maximum ipv4 bgp prefix length of /24 ? Matthew Petach (Oct 05)
- Re: maximum ipv4 bgp prefix length of /24 ? William Herrin (Oct 04)
- Message not available
- Message not available
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- Re: maximum ipv4 bgp prefix length of /24 ? Mark Tinka (Oct 04)
- Re: maximum ipv4 bgp prefix length of /24 ? Owen DeLong via NANOG (Oct 05)
- Re: maximum ipv4 bgp prefix length of /24 ? William Herrin (Oct 05)
- Re: maximum ipv4 bgp prefix length of /24 ? Delong.com via NANOG (Oct 09)
- Re: maximum ipv4 bgp prefix length of /24 ? Matthew Petach (Oct 09)
- Re: maximum ipv4 bgp prefix length of /24 ? Delong.com via NANOG (Oct 10)
- Re: maximum ipv4 bgp prefix length of /24 ? Mark Andrews (Oct 10)
- Re: maximum ipv4 bgp prefix length of /24 ? Delong.com via NANOG (Oct 11)
- Re: maximum ipv4 bgp prefix length of /24 ? Mark Andrews (Oct 11)
- Re: maximum ipv4 bgp prefix length of /24 ? Delong.com via NANOG (Oct 11)
- Re: maximum ipv4 bgp prefix length of /24 ? Mark Andrews (Oct 11)