as-ip-blocks (formerly asn-ip)

📢 New and improved: This repo has been upgraded with a clearer name (as-ip-blocks) and enhanced JSON format. Check out MIGRATION.md for the quick changes needed (plaintext files are unchanged).

Daily-updated datasets of autonomous systems (AS) with active BGP prefix announcements. Only includes AS that have announced at least one prefix within the last 90 days. No APIs, no databases - just simple file downloads.

Each AS gets its own directory with aggregated IPv4 and IPv6 prefixes in both JSON and plaintext formats. Prefixes are aggregated (adjacent and overlapping CIDR blocks are merged into larger blocks where possible). Perfect for firewall rules, network analysis, or tracking what IP ranges belong to specific organizations. Git history lets you see how an AS's announcements change over time.

Available formats: JSON and plaintext

JSON format (includes both IPv4 and IPv6):

{
  "asn": 1234,
  "metadata": {
    "handle": "FORTUM",
    "description": "Fortum",
    "countryCode": "FI",
    "country": "Finland",
    "origin": "authoritative"
  },
  "prefixes": {
    "ipv4": [
      "132.171.0.0/16",
      "137.96.0.0/16",
      "193.110.32.0/21"
    ],
    "ipv6": [
      "2405:1800::/32"
    ]
  }
}

Plaintext format (AS1234 IPv4):

# AS1234 (FORTUM)
# Fortum
#
132.171.0.0/16
137.96.0.0/16
193.110.32.0/21

Plaintext format (AS1234 IPv6):

# AS1234 (FORTUM)
# Fortum
#
2405:1800::/32

Metadata fields:

• countryCode: ISO 3166-1 alpha-2 country code (may be null if unknown)
• country: Country name in English (may be null if unknown)
• origin: Metadata source indicator
  • authoritative: From authoritative source
  • inferred: Inferred from routing information; may be inaccurate
  • overlaid: Metadata overlay from as-overlay applied
  • none: No metadata available

Update notes

• 2026-01-08: AS directories are now removed if no prefixes have been announced in the last 90 days. Historical metadata for removed AS may still be available in as-metadata.
• 2026-01-05: Removed lastAnnounced field to reduce git delta size. This field is still available in as-metadata.
• 2026-01-03: Repository renamed to as-ip-blocks, JSON format changed (subnets → prefixes, metadata nested). See MIGRATION.md for details.
• 2025-08-03: Removed opinionated handle cleanup
• 2023-09-03: Removed PEM certificates from description field

How to use

Download the announced prefixes for a specific autonomous system:

AS1234 in JSON format:

curl https://raw.githubusercontent.com/ipverse/as-ip-blocks/master/as/1234/aggregated.json

AS1234 IPv4 addresses:

curl https://raw.githubusercontent.com/ipverse/as-ip-blocks/master/as/1234/ipv4-aggregated.txt

AS1234 IPv6 addresses:

curl https://raw.githubusercontent.com/ipverse/as-ip-blocks/master/as/1234/ipv6-aggregated.txt

For AS metadata (ASN, handle, description, country code), see as-metadata.

Firewall integration

If you plan to use the routing data for firewalling purposes, have a look at:

• ipset-blacklist - ipset/iptables based Bash script, IPv4 only
• ipverse-tools-crowdsec - Ban prefixes using Crowdsec's cscli command

How do I get the ASN for an IP address?

Check out this blog post: https://blog.jiayu.co/2018/10/quick-url-to-asn-lookups/

Use cases

• Block entire AS at the firewall (goodbye spam-friendly hosting providers)
• Check what routes an AS is announcing (Git history lets you track changes over time)
• Network research and statistical analysis
• Threat hunting and security research
• Figure out which IPs belong to a specific organization
• Pretty much anything where you need to map ASNs to their announced prefixes

Related projects

• as-metadata: Complete AS metadata including lastAnnounced timestamps and additional fields not included in the per-AS files here.
• as-overlay: Autonomous system metadata overlays that supplement and enhance the authoritative data in this repository. When overlay data is applied, entries will have an origin value of overlaid in the JSON format.

Questions or issues?

Head over to the feedback repository if you have questions, issues, or suggestions.

License

This data is released under CC0 1.0 Universal.