AS Macros Index - Browse AS-SETs and Routing Policy Objects

Search for

An AS-SET (AS macro) is a named collection of Autonomous System numbers used to define routing policy, simplifying BGP configuration by grouping related networks. Use rtsak.com to explore and expand AS-SETs.

What is an AS Macro?

An AS-SET (commonly called AS macro) is an Internet Routing Registry (IRR) object that groups AS numbers together. They enable ISPs to express routing policy without enumerating every individual ASN.

Example: AS-GOOGLE includes AS15169 plus all Google-related ASNs. Instead of listing dozens of ASNs in BGP filters, networks reference the single AS-SET.

AS Macro Structure

AS-SETs can contain:

  • Individual AS numbers (e.g., AS15169)
  • Other AS-SETs (nested, enabling hierarchical organization)
  • AS numbers with source suffix (e.g., AS15169:AS-CUSTOMERS)

Naming conventions:

  • Start with AS- prefix
  • Examples: AS-GOOGLE, AS-CLOUDFLARE, AS-HURRICANE

Where AS Macros are Registered

AS-SETs are maintained in Internet Routing Registries:

  • RADB - Routing Assets Database (widely used)
  • RIPE - European registry
  • ARIN - North American registry
  • APNIC - Asia-Pacific registry
  • Level3 - Formerly Level3's IRR
  • ALTDB - Alternative routing database

How AS Macros Work

  1. Definition - Network operator creates an AS-SET in an IRR
  2. Membership - Lists member ASNs and nested AS-SETs
  3. Expansion - Routing tools recursively expand to get all ASNs
  4. Filtering - Upstream providers build BGP prefix filters based on expanded membership

Common Use Cases

  • Customer cone definition - ISPs define AS-CUSTOMERNAME containing all customer ASNs
  • Peering policy - Express which ASNs traffic should be accepted from
  • Prefix filtering - Generate BGP filters from IRR data automatically
  • Documentation - Maintain authoritative list of related networks

How to Use AS Macro Lookup

Enter an AS-SET name (e.g., AS-GOOGLE or AS-CLOUDFLARE) to view:

  • Direct members (ASNs and nested AS-SETs)
  • Recursively expanded member list
  • Reverse membership (which AS-SETs contain this ASN)
  • IRR source and maintainer

FAQ

What's the difference between an AS-SET and an AS number?
An AS number identifies a single network. An AS-SET is a container that groups multiple AS numbers (and other AS-SETs) for routing policy purposes.
How do I create an AS-SET?
Register it in an IRR (like RADB or your RIR's database). You need maintainer access and typically an AS number allocated to you.
Why are AS-SETs called "AS macros"?
Historical terminology. "Macro" describes their function - one name expanding to many ASNs, similar to macros in programming.
How often are AS-SETs updated?
Depends on the maintainer. Large networks may update customer AS-SETs daily. Some remain static for years.
Can AS-SETs be nested infinitely?
Technically yes, but most tools limit recursion depth (typically 10-20 levels) to prevent infinite loops from circular references.