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Your First AS Number

Audience: anyone announcing IPv6 space who is deciding whether they need an AS Number of their own, and what getting one involves. Read PA or PI? first if you do not have address space yet.

Last updated: October 2026

1. Do you need one?

An Autonomous System (AS) Number identifies a network's routing policy on the internet. Every route in the global table has an origin AS, and every ROA names the AS that may originate a prefix.

You do not need your own to announce a prefix. The network that announces it can originate it from its own AS, as long as your ROA names that AS. Cloud providers originate BYOIP space this way, and some VPS providers with BGP sessions do the same for a customer without an AS Number.

You need your own when:

  • you connect to two or more networks (two upstreams, or an upstream and an internet exchange) and want your prefixes to have one origin wherever they are announced; or
  • you want to choose your own routing: which upstreams you use, who you peer with, and what you accept from each.

If you have a single upstream and no plans for a second, you do not qualify yet, and you do not need one.

2. What the RIPE NCC asks for

The RIPE NCC assigns AS Numbers under its AS Number Assignment Policies (ripe-679), which are short. The rule that matters:

"A network must be multihomed in order to qualify for an AS Number."

So an application names at least two peering partners, each with its AS Number and a contact, and gives your routing policy: what you will announce to each and accept from each, written in RPSL for your aut-num object in the RIPE Database. An AS Number comes either directly from the RIPE NCC to its own members, or through a sponsoring LIR for everyone else. The RIPE NCC assigns from a single pool that makes no distinction between 16-bit and 32-bit numbers, so check that any older routing equipment you use supports 32-bit AS Numbers (RFC 6793).

Before you apply, the RIPE Database needs to know who you are: a person or role object for your contacts, and a maintainer (mntner) that you control. Your AS Number is registered under that maintainer, so you, not your sponsor, keep the aut-num object up to date.

3. Getting one through isp6

isp6 sponsors AS Numbers without a membership. The application is self-service:

  1. Verify your account. A mobile number and a photo ID, once, for a one-off fee.
  2. Apply. Your routing policy, your two peering partners with their AS Numbers and contacts, and your RIPE handles and maintainer, which isp6 checks live against the RIPE Database. An organisation also uploads proof of its legal status. You sign the agreements electronically and pay the setup fee.
  3. Review and filing. A person at isp6 reviews the application and files it with the RIPE NCC. RIPE NCC staff evaluate it and decide.
  4. Issue. The AS Number is registered to you, under your maintainer. The yearly sponsorship fee starts on that day, not before.

Prices, in pounds and euros, are on PI space and AS Numbers. An AS Number you already hold can move to isp6 from another sponsoring LIR, and one isp6 sponsors can move to another sponsor later. Either way it stays yours.

4. Once it is issued

Add it to your ROAs before you announce from it. For an isp6 /48, add your new AS Number as an origin on the RPKI tab of the subnet's dashboard page, alongside the AS that announces the prefix today: a /48 can name up to eight. isp6 publishes the ROA, and a route6 object in the RIPE Database for each origin. Once the dashboard shows the new origin published, bring up your own sessions, and remove the old origin when nothing announces from it any more. Changing the origin in one step would make one of the two announcements RPKI-invalid in between.

Keep your aut-num current. Some upstreams build their filters from the RIPE Database, so an aut-num whose import and export lines name your real peers saves a support ticket later. If you announce space on behalf of others, an as-set listing them is what those filters read.

Bring up your sessions. On your side, a BGP session with your own AS Number looks like one with an AS your provider gave you: local as is the line that changes. Ask the provider whether anything changes on theirs. Announcing Your /48 from a VPS with BIRD has a working configuration.

5. Further reading

Ready for your own AS Number?

isp6 sponsors AS Numbers without a membership: verify your account, apply with your routing policy and two peers, and the RIPE NCC assigns the number to you.

PI space and AS Numbers →

This document is provided for informational purposes. Protocol specifications and cloud provider behaviour are subject to change. Consult the linked RFCs and vendor documentation for authoritative, up-to-date information before making architectural decisions.