NetSight
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Network Block Lookup

Look up an IP address, CIDR block or address range and see the registered network around it: holder, network name, type, country, registration dates, abuse contact, CIDR breakdown, every address in the block and the networks that announce it.

What a network block is

IP addresses are handed out in blocks. A regional internet registry allocates a large block to a provider, the provider assigns smaller blocks to customers, and every one of these steps is recorded in a public registry entry. The entry names the holder, the exact first and last address, the type of assignment and a contact for abuse reports.

Enter a single address and you get the smallest registered block around it. Enter a CIDR block or an address range and you get the registered network that contains all of it, plus a list of every address you entered.

What you'll see

  • Holder: the organisation the block is registered to, with its postal address where the registry publishes one.
  • Range and CIDR list: first and last address, the same block written as CIDR prefixes, and the number of addresses.
  • Type and status: for example direct allocation, assigned portable or sub-allocated, with the registration and last change dates.
  • Abuse contact: the address to report spam, attacks or fraud coming from the block.
  • Routing: the network that announces the block on the internet and the prefix it uses.
  • Address list: every address in an IPv4 block, shown on the page for small blocks and as a download up to 65,536 addresses.

When it's useful

  • Finding out who to contact when an address in your logs attacks or spams you.
  • Seeing the whole block behind a single address before writing a firewall or allow list rule.
  • Converting an address range from a registry entry or contract into CIDR notation.
  • Checking who really holds a block before buying, leasing or trusting it.

Questions

Where does the data come from?
Registration data comes from the public registry databases of the five regional internet registries, RIPE NCC, ARIN, APNIC, LACNIC and AFRINIC. The tool asks the registry that is responsible for the address, so the entry is the original one and not a copy.
Why are some contacts missing?
Contacts that are private individuals are never shown, and neither are maintainer objects. Registries publish them, but a lookup tool has no reason to put personal names and addresses on a web page. Organisations and role contacts such as abuse desks are shown.
Why does a larger block show a different owner than the address?
Blocks are nested. The provider holds a large allocation and a customer holds a small piece of it. A single address returns the smallest registered block around it, a CIDR block returns the smallest block that contains all of it, so a wider search can end at the provider.
Why is there no address list for IPv6?
A single IPv6 block usually holds more addresses than there are grains of sand on earth. Listing them is neither possible nor useful, so the tool shows the CIDR blocks and the number of addresses instead.
Who is the registrar of an IP address?
IP addresses have no registrar in the sense of domain names. The registry that allocated the block is shown instead, together with the holder, which is the organisation you would call the owner.
IP Lookup
Instant geolocation, ISP, ASN, abuse history and reputation for any IPv4 or IPv6 address.
WHOIS Lookup
Domain ownership, registrar, nameservers and key dates.
Speed Test
Latency and throughput test against a globally-distributed edge.
ASN Lookup
Holder, announced prefixes, upstreams and downstreams for any AS number, IP or name.