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Updated Jul 15, 2026

Network

Turn one ASN into the CIDR blocks it announces

Resolve one ASN to the IP prefixes it announces.

Agent
Scope an ASN's announced address spaceSeed a CIDR-to-host scanning pipelineMap infrastructure behind an organization

overview

What get-asn-prefixes does

get-asn-prefixes accepts a single autonomous system number passed positionally and returns the CIDR prefixes that ASN announces. One ASN in, concrete address space out.

Those prefixes seed infrastructure mapping: expand to hosts, port-scan live addresses, probe answering services. The node stays narrow; it does not resolve orgs or expand hosts itself.

Trickest runs it as a managed Network node ahead of CIDR reshape and scanning. Feed an ASN from asnmap, then hand the prefix file to mapcidr, decant, or a port scanner.

use cases

Where get-asn-prefixes fits

Scope an ASN's announced address space

Resolve a known ASN to the CIDR prefixes routed behind it, then treat those ranges as the in-scope boundary for the rest of the engagement.

Seed a CIDR-to-host scanning pipeline

Write the prefixes to a file and hand them to a CIDR expander and a port scanner so probing runs against the IP space the ASN announces.

Map infrastructure behind an organization

Start from the ASN you resolved for a company and pull its prefixes to reveal the broader network it operates, including ranges no published hostname points at.

Build an owned-ranges inventory

Run it per ASN across an organization's autonomous systems and collect the prefix files into a single picture of the address space it controls.

reference

get-asn-prefixes inputs and flags

1 inputs
NameTypeFlagDescription
asnSTRING·Autonomous system number to fetch announced IP prefixes for (passed positionally, for example AS64496).

Showing key inputs. get-asn-prefixes exposes 1 inputs in total.

example

Run get-asn-prefixes

get-asn-prefixes · command
# get-asn-prefixes: list announced CIDRs for one ASNget-asn-prefixes AS64496
sample output
192.0.2.0/24198.51.100.0/24198.51.100.0/25198.51.100.128/25203.0.113.0/24203.0.113.0/26203.0.113.64/26203.0.113.128/25

guidance

Choosing get-asn-prefixes

Use when you already have an ASN and need the prefixes it announces. To resolve an org, domain, or IP to an ASN first, run asnmap. To slice or merge the prefixes once you have them, use mapcidr.

asnmap

Resolves an org, domain, ASN, or IP to ranges. Run it ahead of this node when you only have a name, not a number.

mapcidr

Operates on CIDR ranges (split, merge, aggregate). Use it after this node to reshape the prefixes.

decant

Expands CIDR ranges into individual IP addresses. Run it on the prefixes before host-level scanning.

faq

get-asn-prefixes questions

One autonomous system number, passed positionally with no flag. It accepts a single ASN such as AS64496 and returns the prefixes announced under it.

related

More Network tools

  1. asnmap

    Map an organization's network ranges from ASN data.

  2. dnsvalidator

    Validate public DNS resolvers against trusted baselines.

  3. fping

    Parallel ICMP echo sweeps for CIDR ranges and host files.

  4. httprobe

    Probe a domain list for working HTTP and HTTPS servers.

  5. httpx

    A fast and multi-purpose HTTP toolkit that runs multiple probers with reliable, high-throughput results.

  6. mapcidr

    Expand, aggregate, and slice CIDR ranges into host lists.

Run get-asn-prefixes yourself

An ASN feeds get-asn-prefixes, which pulls the announced CIDR blocks and passes them to mapcidr for cleanup before they land as a queryable prefixes output.

Open get-asn-prefixes in the libraryBuild a workflow with it

Facts on this page come from the live Trickest tool library.