Network Tool
BGP View Lookup
Look up ASN, organization, and IP prefix routing information from the global BGP routing table.
Enter an IP address, ASN (e.g. AS15169), or CIDR prefix to look up BGP routing information.
This free BGP lookup tool lets you query Border Gateway Protocol routing data by IP address, ASN, or prefix. It shows you the Autonomous System that originates a prefix, the announced CIDR blocks, and the organization behind an ASN. Data is sourced from RIPEstat, the RIPE NCC's public data analysis platform, and reflects near-real-time routing table state.
What an ASN is and why it matters
An Autonomous System Number (ASN) is a globally unique 32-bit integer assigned by a Regional Internet Registry (ARIN, RIPE NCC, APNIC, etc.) to an organization that operates a routing domain with a single, clearly defined routing policy. BGP is the protocol that interconnects these autonomous systems: each AS announces the IP prefixes it originates or re-advertises, and those announcements propagate across the internet. Knowing an ASN tells you who controls the routing of a given IP block and which upstream providers they peer with.
Prefixes, announcements, and route visibility
A BGP announcement (also called an advertised prefix) is the act of an AS telling its peers: "I can reach this CIDR block." The prefix must be in a global routing table to be visible — private address space (RFC 1918) and unallocated blocks are filtered at internet exchange points. When you look up an IP, this tool finds the most-specific covering prefix in the RIPEstat routing data and shows you the originating ASN, the announcing organization, and related prefixes that same AS is advertising.
How the data is sourced
All routing data comes from RIPEstat, which aggregates BGP table dumps from multiple route collectors in the RIPE NCC infrastructure (part of the RIPE Routing Information Service, RIS). The data reflects what route collectors see from their vantage points and is updated frequently, but it is not a true real-time feed — propagation delays and collector coverage gaps mean occasionally a very new or withdrawn prefix may not yet be reflected. For authoritative allocation data, cross-reference with the relevant RIR's Whois.
Frequently asked questions
What is an ASN?+
An Autonomous System Number is a unique identifier assigned to an organization that operates a BGP routing domain. It tells you who controls the routing policy for a set of IP prefixes. ASNs were originally 16-bit (1–65535); the current 32-bit format (RFC 4893) supports over four billion values.
How do I find the ASN for an IP address?+
Enter the IP address in the lookup field. The tool queries RIPEstat to find the most-specific BGP prefix covering that address and returns the originating ASN and organization.
What are announced prefixes?+
Announced prefixes are the CIDR blocks an AS is actively advertising via BGP to its peers. An AS may originate (own) a prefix or re-announce it on behalf of a customer. The lookup shows all prefixes currently seen from the queried ASN.
Is the BGP data live?+
It is near-real-time — RIPEstat updates its routing data from BGP collectors frequently, but there is a small propagation delay. For operational troubleshooting, treat results as accurate within a few minutes of current routing table state.
Why does an IP show no ASN or prefix?+
The IP may be in private address space (RFC 1918), an unallocated block, or a prefix that is not currently advertised in the global BGP table. Not every allocated address is actively routed.