Ask your upstream providers for a BGP community tag that lowers localpref below 100 within their network. Set that community tag on any backup routes along with your (moderate) path prepending.
The backup upstream will then install that route only if there is no other way to get to your AS. The path prepending remains so that other providers can more quickly install the primary route when it comes back. Those two actions together have always made any backup route behave correctly for me. -Brian > On Mar 25, 2022, at 4:57 PM, Adam Thompson <athomp...@merlin.mb.ca> wrote: > > > Tom, how exactly does someone “ride the 0/0” train in the DFZ? > > I’m connected to both commercial internet and NREN, and unfortunately-long > paths are not uncommon in this scenario, in order to do traffic steering. If > there’s another solution that affects global inbound traffic distributions, > I’d love to hear about it (and so would a lot of my peers in edu). > > If there were a usable way to “dump” the excessively-long path only as long > as a better path was already known by at least one edge router, that might be > workable, but you’d have to keep track of it somewhere to reinstall it if the > primary route went away… at which point you may as well have not dropped it > in the first place. > > -Adam > > Adam Thompson > Consultant, Infrastructure Services > > 100 - 135 Innovation Drive > Winnipeg, MB, R3T 6A8 > (204) 977-6824 or 1-800-430-6404 (MB only) > athomp...@merlin.mb.ca > www.merlin.mb.ca > > From: NANOG <nanog-bounces+athompson=merlin.mb...@nanog.org> On Behalf Of Tom > Beecher > Sent: Friday, March 25, 2022 4:13 PM > To: Paschal Masha <paschal.ma...@ke.wananchi.com> > Cc: nanog <nanog@nanog.org> > Subject: Re: DMARC ViolationAS21299 - 46.42.196.0/24 ASN prepending 255 times > > The best practice with regards to as_path length is to have an edge filter > that dumps any prefix with a length longer than say 10. Depending on the > situation, might even be able to go smaller. > > At a certain point, keeping that route around does nothing for you, just > shoot it and ride the 0/0 train. > > On Fri, Mar 25, 2022 at 4:09 AM Paschal Masha <paschal.ma...@ke.wananchi.com> > wrote: > :) probably the longest prepend in the world. > > A thought though, is it breaking any standard or best practice procedures? > > Regards > Paschal Masha | Engineering > Skype ID: paschal.masha > > ----- Original Message ----- > From: "Erik Sundberg" <esundb...@nitelusa.com> > To: "nanog" <nanog@nanog.org> > Sent: Friday, March 25, 2022 6:43:38 AM > Subject: DMARC ViolationAS21299 - 46.42.196.0/24 ASN prepending 255 times > > If anyone from AS21299 is lurking on Nanog. Please reduce your AS prepends > for 46.42.196.0/24 from 255 prepends to a more reasonable number of prepends > let's say 20. Thanks! > > This is a Kazakhstan register IP Block and ASN > > > > Network Next Hop Metric LocPrf Weight Path > > *> 46.42.196.0/24 x.x.x.x 0 100 0 2914 174 3216 3216 35168 21299 21299 21299 > 21299 21299 21299 21299 21299 21299 21299 21299 21299 21299 21299 21299 21299 > 21299 21299 21299 21299 21299 21299 21299 21299 21299 21299 21299 21299 21299 > 21299 21299 21299 21299 21299 21299 21299 21299 21299 21299 21299 21299 21299 > 21299 21299 21299 21299 21299 21299 21299 21299 21299 21299 21299 21299 21299 > 21299 21299 21299 21299 21299 21299 21299 21299 21299 21299 21299 21299 21299 > 21299 21299 21299 21299 21299 21299 21299 21299 21299 21299 21299 21299 21299 > 21299 21299 21299 21299 21299 21299 21299 21299 21299 21299 21299 21299 21299 > 21299 21299 21299 21299 21299 21299 21299 21299 21299 21299 21299 21299 21299 > 21299 21299 21299 21299 21299 21299 21299 21299 21299 21299 21299 21299 21299 > 21299 21299 21299 21299 21299 21299 21299 21299 21299 21299 21299 21299 21299 > 21299 21299 21299 21299 21299 21299 21299 21299 21299 21299 21299 21299 21299 > 21299 21299 21299 21299 21299 21299 21299 21299 21299 21299 21299 21299 21299 > 21299 21299 21299 21299 21299 21299 21299 21299 21299 21299 21299 21299 21299 > 21299 21299 21299 21299 21299 21299 21299 21299 21299 21299 21299 21299 21299 > 21299 21299 21299 21299 21299 21299 21299 21299 21299 21299 21299 21299 21299 > 21299 21299 21299 21299 21299 21299 21299 21299 21299 21299 21299 21299 21299 > 21299 21299 21299 21299 21299 21299 21299 21299 21299 21299 21299 21299 21299 > 21299 21299 21299 21299 21299 21299 21299 21299 21299 21299 21299 21299 21299 > 21299 21299 21299 21299 21 299 21299 21299 21299 21299 21299 21299 21299 > 21299 21299 21299 21299 21299 21299 i > > > > > > > > > CONFIDENTIALITY NOTICE: This e-mail transmission, and any documents, files or > previous e-mail messages attached to it may contain confidential information > that is legally privileged. If you are not the intended recipient, or a > person responsible for delivering it to the intended recipient, you are > hereby notified that any disclosure, copying, distribution or use of any of > the information contained in or attached to this transmission is STRICTLY > PROHIBITED. If you have received this transmission in error please notify the > sender immediately by replying to this e-mail. You must destroy the original > transmission and its attachments without reading or saving in any manner. > Thank you. > >
