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Comment by diegorbaquero | Hacker News Reader

Great read! I've always wanted to start one too. How did you go about the addressing? Did you purchase IP blocks from Zayo? If you could go technical it would be great.

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I have a /24 from Zayo and a /23 from ARIN for IPv4. For IPv6 I have a /32 IPv6 from ARIN.

If he's using Level 3, he would have to have his own PI-IP block. I'd be interested to hear more about IPv4 and IPv6 in the small ISP world. With 50-100 clients, a single /24 block would serve his current client base.

Why is that? Level3 is one of my upstreams and I've had two /23s from them for a few years. I'm pretty sure they still have some addresses available, although they might be harder to get nowadays.

You can get provider-aggretable (PA) IP addresses from your ISP, but they can only be used with that ISP. You can also get provider-independent (PI) addresses, which you can use and move between ISPs with BGP. If they're using Zayo and Level 3 at the same time, you would need PI-IPs that you can move to the other ISP when one ISP is down.

Or, another option is that they're doing CGNAT on all of their client traffic.

Not true. You do not need PI addresses. You can announce IPs owned by one ISP to another one. Many ISPs will allow you to do this.

> You can get provider-aggretable (PA) IP addresses from your ISP, but they can only be used with that ISP.

Sorry, this is incorrect -- I'm a network engineer and I've been doing exactly this for years. I advertise "Level3 IPs" to other ISPs/peers, I advertise "non-Level3 IPs" to Level3, hell, I even "re-advertise" some of my customers' PI addresses (that they advertise to me) up to Level3.

Actually, I can advertise any prefixes I want via Level3 -- even yours (assuming you had your own).

n.b.: Now, some ISPs may require an LOA (or similar) before they'll accept certain prefixes from you but that's a (easily solved) procedural issue -- not a technical issue.

Sure, there's no technical issue since a prefix is a prefix is a prefix. It's all just bits. If you can convince your upstream/peers to accept a route, there's nobody to stop you. I haven't run an ISP, so maybe I haven't had to push hard enough, but my transit providers' willingness to accept someone else's PA block has been nil.

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