TTR Networks

Intermediate · IRR, RPSL and AS-SETs · section 4 of 8

aut-num and routing policy

✓ Lab-tested 17 October 2026 on IRRd 4.5.3, bgpq4 1.9, PostgreSQL 16, Redis 7

An aut-num object describes an autonomous system. RIR-assigned ASNs have one in the RIR database, maintained jointly by the RIR (for example RIPE-NCC-END-MNT) and the holder.

RPSL was designed to describe routing policy as well as data. The import: and export: attributes, and their multiprotocol versions mp-import:/mp-export: for IPv6, say what an AS accepts from and announces to each neighbour:

import:  from <peer-as> accept <filter>
export:  to <peer-as> announce <filter>

A filter can be ANY, an ASN, an as-set, a route-set or an expression combining them.

In practice, few networks keep import/export accurate or generate config from them. The part that matters day to day is the export towards your upstreams and peers: it documents which as-set to expand to build a filter for you. Most networks now also publish that set name in PeeringDB (the IRR as-set/route-set field), which is where peers look first.

member-of: is how an aut-num asks to join an as-set from the member's side. The set must opt in with mbrs-by-ref: (covered next).

An aut-num with routing policy
aut-num:        AS64500
as-name:        EXAMPLE-NET
descr:          Example Network
org:            ORG-EX1-RIPE
member-of:      AS64496:AS-CUSTOMERS
import:         from AS64496 accept ANY
export:         to AS64496 announce AS64500:AS-CUSTOMERS
import:         from AS64501 accept AS64501:AS-CUSTOMERS
export:         to AS64501 announce ANY
mp-import:      afi ipv6.unicast from AS64496 accept ANY
mp-export:      afi ipv6.unicast to AS64496 announce AS64500:AS-CUSTOMERS
admin-c:        EX123-RIPE
tech-c:         EX123-RIPE
status:         ASSIGNED
mnt-by:         RIPE-NCC-END-MNT
mnt-by:         EXAMPLE-MNT
source:         RIPE
  • Lines 1–2: Primary key and a short name. as-name is what tools and looking glasses display.
  • Line 5: Asks to join the upstream's set. It only takes effect if that set lists EXAMPLE-MNT (or ANY) in mbrs-by-ref.
  • Lines 6–7: Towards the upstream: accept everything, announce our customer cone. Line 7 is what tells AS64496 which set to expand for its filter on us.
  • Lines 8–9: Towards our customer: accept their cone, send them a full table.
  • Lines 10–11: The IPv6 equivalents. mp-import/mp-export take an afi to say which address family they apply to.
  • Lines 14–16: status and RIPE-NCC-END-MNT are added by the RIR for ASNs it assigned. You maintain the object alongside it.

Check your understanding

Where do most peers look today to find which as-set to expand for your network?

  • Your as-name attribute
  • The IRR as-set/route-set field in your PeeringDB record
  • Your inetnum object
  • Your mntner object