nanog mailing list archives
Re: Newbies Question: Do I really need to sacrifice Prefix-aggregation to do BGP Load-sharing? (the case of Multi-homed + Multi-routers + Multi-upstreams)
From: William Herrin <bill () herrin us>
Date: Tue, 18 Oct 2022 23:40:26 -0700
On Tue, Oct 18, 2022 at 11:27 PM Pirawat WATANAPONGSE via NANOG <nanog () nanog org> wrote:
- Two upstreams (See the following lines), fully cross-connected to our gateways - One (pure) commercial ISP - One academic consortium ISP (who actually uses the above-mentioned commercial ISP as one of its upstreams as well) My current “situation”: - All inbounds “flock” in through the commercial ISP, overflowing the bandwidth; since (my guess) the academic ISP also uses that commercial ISP as its upstream, there is no way for its path to be shorter.
This is what "prepends" are for. You make the AS path sent to the commercial ISP longer by adding extra copies of your own AS to the front. This causes the AS path via the consortium to be the same length or even shorter if you prefer. By default, BGP prefers the most specific prefix first and then the shortest AS path second. Depending on the ISP you may also need to "community" to tell it not to prefer the direct path with you (which they may have done with a localpref). But start with the prepends and see what happens. Regards, Bill Herrin -- For hire. https://bill.herrin.us/resume/
Current thread:
- Newbies Question: Do I really need to sacrifice Prefix-aggregation to do BGP Load-sharing? (the case of Multi-homed + Multi-routers + Multi-upstreams) Pirawat WATANAPONGSE via NANOG (Oct 18)
- Re: [External] Newbies Question: Do I really need to sacrifice Prefix-aggregation to do BGP Load-sharing? (the case of Multi-homed + Multi-routers + Multi-upstreams) Hunter Fuller via NANOG (Oct 18)
- Re: Newbies Question: Do I really need to sacrifice Prefix-aggregation to do BGP Load-sharing? (the case of Multi-homed + Multi-routers + Multi-upstreams) William Herrin (Oct 18)
- RE: Newbies Question: Do I really need to sacrifice Prefix-aggregation to do BGP Load-sharing? (the case of Multi-homed + Multi-routers + Multi-upstreams) Kevin Burke (Oct 19)
- Re: Newbies Question: Do I really need to sacrifice Prefix-aggregation to do BGP Load-sharing? (the case of Multi-homed + Multi-routers + Multi-upstreams) Jay Hennigan (Oct 19)
- Re: Newbies Question: Do I really need to sacrifice Prefix-aggregation to do BGP Load-sharing? (the case of Multi-homed + Multi-routers + Multi-upstreams) Douglas Fischer (Oct 19)