nanog mailing list archives
Re: maximum ipv4 bgp prefix length of /24 ?
From: Mark Tinka <mark@tinka.africa>
Date: Sat, 30 Sep 2023 08:59:54 +0200
On 9/29/23 22:56, William Herrin wrote:
Actually, BGP can swing that. Routing involves two distinct components: the routing information base (RIB) and the forwarding information base (FIB). BGP is part of the RIB portion of that process. It's always implemented in software (no hardware acceleration). It's not consulted per-packet, so as long as the update rate is slow enough for the CPU to keep up and there's enough DRAM (which is cheap and plentiful these days) to hold the entire thing, there's no particular upper bound to the number of routes.
Not unless you are running BGP Add-Paths in its extreme guise to consider all available paths, and then there is the chance you could push your RAM and CPU into unknown territory, depending on the platform, code and control plane you've got.
The limiting factor is the FIB. The FIB is what is implemented with hardware acceleration on high-end routers in order to achieve large packet-per-second (PPS) numbers. It relies on storage hardware which is both faster and more expensive than DRAM. Consequently it has much less capacity to store information than DRAM. Currently shipping equipment intended for BGP backbone use can manage 1M to 2M routes in the hardware-accelerated FIB regardless of the amount of DRAM on the machine.
There are line cards out there today that are able to hold 10 million routes in FIB.
Mark.
Current thread:
- Re: maximum ipv4 bgp prefix length of /24 ?, (continued)
- Re: maximum ipv4 bgp prefix length of /24 ? Owen DeLong via NANOG (Sep 28)
- Re: maximum ipv4 bgp prefix length of /24 ? Owen DeLong via NANOG (Sep 28)
- RE: maximum ipv4 bgp prefix length of /24 ? Vasilenko Eduard via NANOG (Sep 28)
- Re: maximum ipv4 bgp prefix length of /24 ? VOLKAN SALİH (Sep 29)
- RE: maximum ipv4 bgp prefix length of /24 ? Jason Baugher (Sep 29)
- Re: maximum ipv4 bgp prefix length of /24 ? VOLKAN SALİH (Sep 29)
- Re: maximum ipv4 bgp prefix length of /24 ? Tom Beecher (Sep 29)
- Re: maximum ipv4 bgp prefix length of /24 ? Seth Mattinen via NANOG (Sep 29)
- Re: maximum ipv4 bgp prefix length of /24 ? Collider (Sep 29)
- Re: maximum ipv4 bgp prefix length of /24 ? William Herrin (Sep 29)
- Re: maximum ipv4 bgp prefix length of /24 ? Mark Tinka (Sep 30)
- Re: maximum ipv4 bgp prefix length of /24 ? Owen DeLong via NANOG (Sep 29)
- Re: maximum ipv4 bgp prefix length of /24 ? Owen DeLong via NANOG (Sep 29)
- RE: maximum ipv4 bgp prefix length of /24 ? Vasilenko Eduard via NANOG (Sep 28)
- Re: maximum ipv4 bgp prefix length of /24 ? Owen DeLong via NANOG (Sep 29)
- Re: maximum ipv4 bgp prefix length of /24 ? Collider (Sep 29)
- Re: maximum ipv4 bgp prefix length of /24 ? Owen DeLong via NANOG (Sep 29)
- Re: maximum ipv4 bgp prefix length of /24 ? Daniel Corbe (Sep 29)
- Re: maximum ipv4 bgp prefix length of /24 ? Owen DeLong via NANOG (Sep 29)
- Re: maximum ipv4 bgp prefix length of /24 ? Owen DeLong via NANOG (Sep 28)
- Re: maximum ipv4 bgp prefix length of /24 ? VOLKAN SALİH (Sep 29)