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> They'd need multiple ASNs for each of these network islands then, though No they wouldn’t. They could connect to local transit/IXs in each region and just ad
by ccakes 3y ago
> They'd need multiple ASNs for each of these network islands then, though
No they wouldn’t. They could connect to local transit/IXs in each region and just advertise the regional networks.
- lxgr 3y agoOh, I thought it wasn't possible to announce multiple isolated networks on the same ASN without interconnecting them, since ASNs are the routing granularity of BGP?
- ericpauley 3y agoOne counterexample to this would be Amazon, who have IPs globally under one ASN. While they do have a global backhaul, it seems unlikely they accept traffic for any IP anywhere and route it all on the backhaul.
- dilyevsky 3y ago> accept traffic for any IP anywhere and route it all on the backhaul. This is actually what they do when you enable Global Accelerator which is a paid feature. In GCP they have similar concept called “Premium Tier”
- ericpauley 3y agoTrue! In my post I meant for all traffic.
- zajio1am 3y agoAS is basic granularity in BGP in the sense that one ASN should not be multiple times in AS PATH, and it is generally assumed that ASs are internally connected (although for non-transit networks, this could be workarounded in several ways) But basic routing entity in BGP is still prefix/route, and different routes of one AS can be announced in different ways.
- Hikikomori 3y agoFor something remote it just looks like two different prefixes with a different path to reach them. It's even a commonly used technique for multi homing so you can control which peer ingress traffic comes in on for a specific prefix.
- midasuni 3y agoIf I have AS22, advertising 2.2.2.0/24 out of NY, then I can reach 1.1.1.1, great I then have 2.2.3.0/24 advertised out of Frankfurt with the same AS. Again I have transit. I can reach 1.1.1.1. How does a packet from 2.2.2.1 reach 2.2.3.1 -— 2.2.3.0 won’t be advertised by the transit to me in NY as it thinks I’ve already got the route, after all it originated from my AS.
- ericpauley 3y agoPresumably since these IPs are in the same AS the operator can implement custom routing logic, since they control the routing on both sides.
- zajio1am 3y agoOn BGP protocol level, the loop check is on the receiving side - received paths are scanned for local ASN. The transit may not send you your routes with your ASN due to how its policies are configured, but that is configurable, not protocol-level issue. And most BGP implementations have knobs to disable the loop check, so on your side you could just disable it.
- Hikikomori 3y agoThey could have something to connect their sites, or even tunnel between them over their transit. But if they only have customers on their network, likely behind nat, they don't need to reach each other.
- kiallmacinnes 3y agoPeer to peer? Self hosted stuff? (not sure how these work with starlink specifically, but - they should work, even if for whatever reason they don't)
- Hikikomori 3y agoAfaik you don't get your own public IPv4 address on Starlink.
- 3y ago