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 fischerdouglas at
Wed Oct 19 21:30:14 UTC 2022

I imagine it's an ISP you are talking about, where the traffic is mostly

Hire transit companies that have good traffic engineering community
- Selective prepending or seletive no-export by:
-> Type of peer.
-> Geographic location of their routers.
-> ASN specific.

And then you can get the best out of every transit.
And so the bandwidth balancing will happen not based on your network
prefixes, but based on how the origins see your network.

DO NOT HIRE transit companies that arbitrarily remove all the communities
you mark on the routes you advertise.
By targeting communities with ASNs that are 2 or 3 hops away from the AS
you can also influence how the rest of the world views your network.
And most (not all) of the companies that remove the communities you tag do
this to force you to use what they choose and not what you think is best
for your network.

Em qua., 19 de out. de 2022 03:31, Pirawat WATANAPONGSE via NANOG <
nanog at> escreveu:

> Dear Guru(s),
> My apologies if these questions have already been asked;
> in that case, please kindly point me to the answer(s).
> I hope the following information sufficiently describes my current
> "context":
> - Single customer: ourselves
> - One big IPv4 block + one big IPv6 block
> - Native Dual-Stack, Non-tunneling
> - Non-transit (actually, a “multi-homed Stub”)
> - “All-green” IRR & RPKI registered (based on IRRexplorer report)
> - Fully-aggregated route announcement (based on CIDR report)
> - Two (Cisco) gateway routers on our side
> - 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.
> Questions:
> 1. Do I really have to “de-aggregate” the address blocks, so I can do the
> “manual BGP load-sharing”?
> I hate to do it because it will increase the global route-table entries,
> plus there will be IRR & RPKI “hijack gaps” to contend with at my end.
> 2. If the answer to the above question is definitely “yes”, please point
> me to the Best-Practice in doing the “manual BGP load-sharing (on Cisco)”.
> Right now, all I have is:
> Thanks in advance for all the pointers and help given (off mailing-list is
> also welcome).
> Best Regards,
> Pirawat.
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