Techniques to influence inbound (download) traffic across multiple IXPs with /24 prefixes
Hi everyone, Hope you’re doing well. I’d like to ask how you approach inbound traffic engineering (download traffic) when you’re connected to multiple IXPs (some local, some remote) and you only have small prefixes (e.g., /24), so announcing more/less specifics isn’t really an option. In that scenario, what methods have worked for you besides simple AS-path prepending (e.g., no prepend on local IX, prepend 1 on the closest remote IXP, prepend 2 on the next, etc.)? Thanks in advance for any guidance or real-world examples. -- Salvador
Hi, On Wed, Jan 07, 2026 at 11:54:14AM -0500, Salvador Bertenbreiter wrote:
Hope you???re doing well. I???d like to ask how you approach inbound traffic engineering (download traffic) when you???re connected to multiple IXPs (some local, some remote) and you only have small prefixes (e.g., /24), so announcing more/less specifics isn???t really an option.
"don't connect to remote IXPs" is what works nicely for us. After all, that's what we pay our transit for. Gert Doering -- NetMaster -- have you enabled IPv6 on something today...? SpaceNet AG Vorstand: Sebastian v. Bomhard, Karin Schuler, Sebastian Cler Joseph-Dollinger-Bogen 14 Aufsichtsratsvors.: Dr. Frank Thiäner D-80807 Muenchen HRB: 136055 (AG Muenchen) Tel: +49 (0)89/32356-444 USt-IdNr.: DE813185279
From: Salvador Bertenbreiter <salvadorb@gmail.com> Sent: Wednesday, January 7, 2026 5:54 PM To: routing-wg@ripe.net Subject: [routing-wg] Techniques to influence inbound (download) traffic across multiple IXPs with /24 prefixes Hi everyone, Hope you’re doing well. I’d like to ask how you approach inbound traffic engineering (download traffic) when you’re connected to multiple IXPs (some local, some remote) and you only have small prefixes (e.g., /24), so announcing more/less specifics isn’t really an option. In that scenario, what methods have worked for you besides simple AS-path prepending (e.g., no prepend on local IX, prepend 1 on the closest remote IXP, prepend 2 on the next, etc.)? Thanks in advance for any guidance or real-world examples. Hi Salvador! As Gert said: avoid “remote” peerings. If you really need the remote peerings you probably want to connect to a specific peer. So do not peer with the IX route server but only peer bilateral with the important AS. (Or use the BGP communities of the IX route servers to “no-announce” or “prepend” your prefix selectively to certain peers”). Regards Klaus [1] For example: AMS-IX Router Servers offer these communities: https://www.ams-ix.net/ams/documentation/ams-ix-route-servers
I've used my fair share of Remote IXP's as I do not afford to use local ones. Only thing I'd do in your scenario is to prepend the announcement to the IXP. Or use the IXP's communities if it has any, to lower the local preference of the route, or not export it to certain peers I don't want going over the IXP (ussualy 0,asn works for most) Remote IXP's are a pain to manage, and for most production networks I'd suggest to just avoid them unless strictly necessary for some reason. Regards, Lungu Ștefan-Gabriel | AS205941. ________________________________ From: Salvador Bertenbreiter <salvadorb@gmail.com> Sent: Wednesday, January 7, 2026 6:54 PM To: routing-wg@ripe.net Subject: [routing-wg] Techniques to influence inbound (download) traffic across multiple IXPs with /24 prefixes Hi everyone, Hope you’re doing well. I’d like to ask how you approach inbound traffic engineering (download traffic) when you’re connected to multiple IXPs (some local, some remote) and you only have small prefixes (e.g., /24), so announcing more/less specifics isn’t really an option. In that scenario, what methods have worked for you besides simple AS-path prepending (e.g., no prepend on local IX, prepend 1 on the closest remote IXP, prepend 2 on the next, etc.)? Thanks in advance for any guidance or real-world examples. -- Salvador
participants (5)
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Gert Doering -
Klaus Darilion -
Lungu Stefan -
Randy Bush -
Salvador Bertenbreiter