I've been running BGP on Oracle Cloud free tier for two years now. Pro tip: if you're not paying for a public ASN, you're not really participating in the internet. You're just LARPing as a network operator.
Here's how actual peering works:
1. Get yourself a public ASN from your RIR. Costs money. Means commitment.
2. Lease address space or bring your own PI blocks.
3. Establish bilateral peering with real networks who care about your routing policy.
4. Register in PeeringDB. Show up at IXPs. Shake hands.
Private ASNs (64512-65534, 4200000000-4294967294) let you hide behind your upstream like a child holding their parent's hand. Your AS path gets stripped at the first real peer. Heads up: nobody on the other end knows you exist. You're just a configuration line in someone else's router.
The only legitimate use I've seen is a large enterprise with dozens of edge sites that never need unique identity. Even then, they're admitting they don't care about path diversity or policy control.
Real networks have real ASNs. Everything else is cosplay.
— Olya