nanog mailing list archives
Re: "Tactical" /24 announcements
From: William Herrin <bill () herrin us>
Date: Thu, 12 Aug 2021 10:29:08 -0700
On Thu, Aug 12, 2021 at 10:19 AM William Herrin <bill () herrin us> wrote:
On Thu, Aug 12, 2021 at 9:41 AM Hank Nussbacher <hank () interall co il> wrote:On 12/08/2021 17:59, William Herrin wrote:If you prune the routes from the Routing Information Base instead, for any widely accepted size (i.e. /24 or shorter netmask) you break the Internet.How does this break the Internet? I would think it would just result in sub-optimal routing (provided there is a covering larger prefix) but everything should continue to work. Clue me in, please.A originates 10.0.0.0/16 to paid transit C B originates 10.0.1.0/24 also to paid transit C C offers both routes to D. D discards 10.0.1.0/24 from the RIB based on same-next-hop You peer with A and D. You receive only 10.0.0.0/16 since A doesn't originate 10.0.1.0/24 and D has discarded it. You send packets for 10.0.1.0/24 to A (the shortest path for 10.0.0.0/16), stealing A's paid transit to C to get to B. Unless A filters C-bound packets purportedly from 10.0.1.0/24.
I mashed this sentence together wrong. I meant say: "Unless A filters packets from peers which would use their paid transit," a common policy restriction placed on settlement-free peering.
B doesn't currently transit for A so from B's perspective that's not an allowed path. In which case, your path to 10.0.1.0/24 is black holed. D broke the Internet. If packets from you reach A at all, they do so through an unpermitted path.
-- William Herrin bill () herrin us https://bill.herrin.us/
Current thread:
- Re: "Tactical" /24 announcements, (continued)
- Re: "Tactical" /24 announcements Lukas Tribus (Aug 09)
- Re: "Tactical" /24 announcements Tom Hill (Aug 11)
- Re: "Tactical" /24 announcements Lukas Tribus (Aug 11)
- Re: "Tactical" /24 announcements Jon Lewis (Aug 11)
- Re: "Tactical" /24 announcements Tom Hill (Aug 12)
- Re: "Tactical" /24 announcements William Herrin (Aug 12)
- Re: "Tactical" /24 announcements Hank Nussbacher (Aug 12)
- Re: "Tactical" /24 announcements Amir Herzberg (Aug 12)
- Re: "Tactical" /24 announcements Mark Tinka (Aug 13)
- Re: "Tactical" /24 announcements William Herrin (Aug 12)
- Re: "Tactical" /24 announcements William Herrin (Aug 12)
- Re: "Tactical" /24 announcements Amir Herzberg (Aug 12)
- Re: "Tactical" /24 announcements William Herrin (Aug 12)
- Re: "Tactical" /24 announcements Baldur Norddahl (Aug 12)
- Re: "Tactical" /24 announcements Amir Herzberg (Aug 12)
- Re: "Tactical" /24 announcements Baldur Norddahl (Aug 13)
- Re: "Tactical" /24 announcements William Herrin (Aug 13)
- Re: "Tactical" /24 announcements Amir Herzberg (Aug 13)
- Re: "Tactical" /24 announcements Tom Beecher (Aug 13)
- Re: "Tactical" /24 announcements Amir Herzberg (Aug 13)
- Re: "Tactical" /24 announcements Masataka Ohta (Aug 14)
- Re: "Tactical" /24 announcements Tom Hill (Aug 11)
- Re: "Tactical" /24 announcements Lukas Tribus (Aug 09)