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 <kburke () burlingtontelecom com>]

The inbound traffic will be determined by how the Tier 1’s decide to route, as you are observing they will pick either 
you or your other upstream.  Traffic engineering as the Tier 3 carrier you have described has this kind of unexpected 
traffic routing.  As you have obviously already tried common BGP traffic engineering tool of AS Padding your left with 
next worst option.

Best of luck!

Kevin Burke
802-540-0979
Burlington Telecom
200 Church St, Burlington, VT

From: NANOG <nanog-bounces+kburke=burlingtontelecom.com () nanog org> On Behalf Of Pirawat WATANAPONGSE via NANOG
Sent: Wednesday, October 19, 2022 2:28 AM
To: nanog () nanog org
Subject: Newbies Question: Do I really need to sacrifice Prefix-aggregation to do BGP Load-sharing? (the case of 
Multi-homed + Multi-routers + Multi-upstreams)

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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:
https://www.cisco.com/c/en/us/support/docs/ip/border-gateway-protocol-bgp/13762-40.html#anc52

Thanks in advance for all the pointers and help given (off mailing-list is also welcome).


Best Regards,

Pirawat.