Bogon & anycast check
Checks whether an IP comes from a bogon range (reserved/unallocated) and whether it is operated via anycast — with explanation plus ASN and RIR context.
How this tool works
The bogon & anycast check sheds light on two technical properties of an IP address that are often misunderstood in practice. Bogon denotes addresses from reserved or not-yet-allocated ranges that should not appear as a source on the public internet — if you do see them, it often points to spoofing or misconfiguration. Anycast denotes an address announced simultaneously at many locations worldwide, so requests are routed automatically to the nearest node (typical for DNS resolvers and CDNs). The tool shows both states clearly and complements them with ASN and RIR context. An empty field checks your own IP.
Typical use cases
- Spot a source IP from a bogon range in the server log that hints at spoofing
- Check whether a DNS resolver or CDN endpoint is operated via anycast
- Understand why the same IP responds at different speeds depending on location (anycast)
- Filter out reserved or unallocated address ranges in an evaluation
- Classify the ASN and RIR context of a technically conspicuous IP
Frequently asked questions
What exactly is a bogon address?
An IP from a range that is either reserved for special purposes (e.g. private networks, documentation, loopback) or not yet allocated to an RIR. Such addresses should not appear as a sender on the public internet.
Why is a bogon source IP suspicious?
Because a correctly routed public connection should not have a bogon source address. If it appears, it is often a sign of IP spoofing, misconfigured devices or faulty logging.
What does anycast mean?
The same IP address is announced from multiple locations worldwide. Routing directs each request to the topologically nearest node. This improves speed and resilience and is typical for large DNS resolvers and CDNs.
Why is the location of an anycast IP often wrong?
Because an anycast address exists in many places at once, a single geo estimate can only show one of them. With anycast the location should therefore be read with particular caution.
Are the queried IPs stored?
No. The query is processed in memory and not stored for tracking purposes. The page sets no cookies; our own cookieless reach measurement records no values you enter.
How reliable is anycast detection?
It is based on routing data and known networks and is a good hint, but not proof. Some anycast setups cannot be unambiguously detected from the open data.
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