An Autonomous System Number (ASN) uniquely identifies a network that controls a set of IP prefixes and exchanges routing information over BGP — typically an ISP, hosting provider, or large organization.

How do you map an IP to an ASN?

We query Team Cymru’s IP-to-ASN service over DNS, which returns the originating ASN, the announced BGP prefix, the assigning registry, and the country for the address.

Can I look up an AS number directly?

Yes. Enter a value like AS15169 or 15169 and the tool returns that autonomous system’s registered name, country, registry, and allocation date.

Why does an IP show a different ASN than I expected?

Large organizations often host services inside a cloud or CDN provider’s network, so the address is announced from the provider’s ASN even though the brand differs. The ASN reflects who routes the traffic.

Is the ASN data real-time?

It is derived from recent BGP routing observations, so it tracks how the address is currently announced. Very recent routing changes can take a short time to propagate into the dataset.

Does the lookup run on your servers?

Yes. ToolsHub queries the IP-to-ASN routing service from its servers for the address or AS number you submit and returns the result.

ASN Lookup

Enter an IP address or AS number to see its ASN, network operator, prefix, and country.

Updated June 2026

IP address or AS number

Server processing — your query is handled securely on our servers.

How to use ASN Lookup

The ASN Lookup tool maps an IP address — or an autonomous system number you already have — to the network that announces it on the global routing table. Every block of public IP space is originated by an Autonomous System (AS), identified by a number such as AS13335, and operated by an ISP, hosting company, or large enterprise. Looking up the ASN tells you who really runs the address: the network name, the specific BGP prefix the address falls inside, the regional internet registry that assigned it, and the country of allocation. It is an essential first step when investigating abuse, profiling infrastructure, or understanding how traffic is routed across the internet.

Enter an IPv4 or IPv6 address, or an AS number like AS15169.
Click Lookup to query the IP-to-ASN routing data.
Read the originating ASN, network name, and announced prefix.
Note the assigning registry and country for the allocation.
Use the AS number to pivot into further routing or WHOIS research.

How IP-to-ASN mapping works

Autonomous Systems advertise the IP prefixes they control using the Border Gateway Protocol (BGP). Public route collectors observe these advertisements and record which ASN originates each prefix. To map an IP to its ASN, this tool queries Team Cymru’s IP-to-ASN service over DNS, which returns the origin ASN, the most specific prefix covering the address, the assigning registry, and the allocation date. Because the data is derived from live BGP, it reflects how the address is actually routed today rather than a static ownership database.

ASN vs WHOIS — what each tells you

An ASN identifies the network that routes an address, while IP WHOIS records the organization an address block is registered to. They often point to the same company, but not always: a customer may use IP space announced from their provider’s ASN, or a large operator may route many registered organizations. Checking both gives a fuller picture — the ASN shows who carries the traffic, and WHOIS shows who is administratively responsible.

Regional internet registries
Registry	Region
ARIN	North America
RIPE NCC	Europe & Middle East
APNIC	Asia-Pacific
LACNIC	Latin America
AFRINIC	Africa

Glossary

ASN: Autonomous System Number — a unique identifier for a network on the internet.
BGP: Border Gateway Protocol, used by networks to advertise the IP prefixes they route.
Prefix: A block of IP addresses announced together, written in CIDR form like 1.1.1.0/24.
RIR: Regional Internet Registry that allocates IP space and ASNs within a region.
Origin AS: The autonomous system that originates a prefix into the global routing table.

Frequently Asked Questions

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Why use ASN Lookup?

Identify the network operator and ASN behind any public IP address
See the exact BGP prefix that an address is announced from
Find the regional registry (ARIN, RIPE, APNIC) and country of allocation
Pivot from an IP to its AS number for deeper routing investigation

Common use cases

Determine which hosting provider or ISP owns an IP seen in server logs
Investigate the network behind a suspicious or abusive address
Confirm the ASN of a CDN edge node when debugging routing or geolocation
Map the prefixes and registry of a competitor’s hosting infrastructure
Verify that an IP belongs to the ASN you expect before allow-listing it

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