How to Read an IP Prefix (CIDR) Lookup
An IP prefix is a range of addresses written in Classless Inter-Domain Routing (CIDR) notation, such as 192.0.2.0/24. An IP Lens prefix result explains the range, its size, and the registered organizations and networks observed announcing routes to it. A routing announcement tells other networks that traffic can reach an address range through the announcing network. Networks exchange these announcements using Border Gateway Protocol (BGP). Special-purpose prefixes also explain their reserved use and whether they are normally reachable over the public Internet.
How should I read prefix normalization and route relationships?
Why does 192.168.1.42/24 become 192.168.1.0/24?
A /24 keeps the first 24 bits as the network and leaves the last eight bits for addresses inside it. The .42 part is therefore a host value, not the start of the range. The standard form of a range starts at its first address; this is called its canonical prefix. IP Lens converts (normalizes) 192.168.1.42/24 to the standard network address 192.168.1.0/24, which spans 192.168.1.0 through 192.168.1.255.
What do exact, covering, and more-specific mean?
For a query such as 1.1.1.0/24, the relationship compares each range in the routing information with the queried range:
- Exact: 1.1.1.0/24 is the same range.
- Covering: 1.1.0.0/16 is broader and contains the queried /24.
- More-specific: 1.1.1.0/25 is narrower and covers only part of the queried /24.
These labels describe range containment only. They do not establish registration, route authorization, or the full path taken by traffic.
Why can a prefix result omit a section?
Every prefix result shows the range in its standard form and its boundaries, while Registered Owners, BGP Announcements, individual Addresses, and the same-family special-purpose reference appear only when they apply and usable data is available. A missing Registered Owners or BGP Announcements section can mean that no record matched or that a lookup supplied no usable value. Prefix pages do not show an incomplete-data banner, so treat an absent section as unknown rather than as a negative finding.
An exact special-purpose block is a deliberate exception: IP Lens suppresses Registered Owners and the individual Addresses list on that result, even when the block contains 256 addresses or fewer.
What do Registered Owners show?
Registered Owners come from public registration records that cover the queried prefix or describe a narrower prefix inside it. A broad prefix can contain records for several holders. IP Lens groups records for the same holder and lists the registered prefixes associated with each group.
IP Lens shows at most 100 registered prefixes and displays a notice when a broader result is partial. Registration identifies the holder listed by a registry. It does not prove who announces the prefix, who uses every address, or where the network is physically located. See IP ownership and ASNs.
Owner
The organization or holder named by the registration source.
Handle
The registry identifier for the holder. Handles are interpreted within the listed registry.
Country
The country code attached to the registration record. It is administrative registration data, not a precise location for the network or its users.
Address
The public postal address supplied for the registered holder when the source provides one.
Registry
The Regional Internet Registry associated with the registration record. It identifies the responsible registry context, not how IP Lens obtained the data.
Registered Prefix
The exact network covered by the registration record. A broad query can contain several of these prefixes.
Delegated Prefix
A broader allocation or delegation associated with the registered prefix when the source provides one.
What does the IP prefix section mean?
Every prefix page starts with the range in its standard form and its boundaries. A longer prefix length means a smaller address range: for example, an IPv4 /24 contains 256 addresses, while a /25 contains 128. See IP ranges and CIDR for how prefix lengths divide IPv4 and IPv6 address space.
IP Prefix (CIDR)
The range written in Classless Inter-Domain Routing (CIDR) notation, starting at its first address. If your search uses another address within the range, IP Lens converts it to that standard form. The changing part of the address within a range is called the host bits.
Subnet Mask
The IPv4 prefix length written as a dotted-decimal subnet mask. IPv6 prefixes omit this field.
Address Count
The mathematical number of addresses covered by the prefix, not the number assigned or active.
IP Range
The lowest and highest addresses included in the queried prefix.
Subnet calculator
Open the IP subnet calculator for the conventionally usable IP range, IPv4 Address Range as Long, wildcard masks, adjacent networks, and representations, or choose a cloud-provider calculator for provider reservations.
Why does IP Lens list individual addresses?
For a non-special prefix containing 256 addresses or fewer, IP Lens lists every address and links to its result page. An exact special-purpose block intentionally omits this list even when it contains 256 addresses or fewer. Searching for an address in a special-purpose range redirects to the result for that reserved block instead. Larger ranges also omit the list to keep the page bounded; the IP Range still shows the full range.
Address
One address contained in the queried prefix.
What do the BGP Announcements show?
This table uses the routing information currently available in IP Lens to show ranges and their announcing networks. Each network is identified by an Autonomous System Number (ASN). The ranges can match, contain, or sit inside the queried range. The data may combine adjacent or overlapping ranges into larger ones (aggregation), so a row does not necessarily represent a single BGP update. It is not a live, universal view, does not show the complete AS path, and does not prove address-space ownership. See IP ownership and ASNs.
One prefix can be associated with multiple origin ASNs in the source. IP Lens shows at most 100 matching prefixes and displays a notice when additional more-specific entries are omitted. If time is important, verify the event against a BGP archive for that time rather than assuming the current page reproduces the earlier routing view.
Announced Prefix
The range found in the routing information currently available in IP Lens. It can be the queried prefix, a broader covering entry, or a narrower entry inside the query.
Relationship
Exact is the same prefix; Covering is a broader route containing the query; More specific is a narrower route contained by the query.
Origin ASN
The Autonomous System Number associated with the prefix as its observed origin. Follow it to inspect that network. This field does not show intermediate networks in the AS path.
Description
The source's name or handle for the origin Autonomous System.
Country
The country attached to the origin network's metadata. It is not the location of every address covered by the route.
First Address
The lowest address in the announced prefix, which can differ from the queried prefix's boundary.
Last Address
The highest address in the announced prefix, which can differ from the queried prefix's boundary.
Is this a Special-Purpose Address Block?
When the queried prefix exactly matches a private, local, reserved, documentation, or other special-purpose block, the first card names that purpose, adds its public-routing expectation, and retains the standard prefix details described above. The result intentionally omits Registered Owners and the individual Addresses list, even when the block contains 256 addresses or fewer. BGP Announcements and a reference list of other special-purpose blocks in the same address family can still appear. See Special-purpose IP blocks.
Public routing
Whether the block is expected to be globally reachable. This is a routing expectation, not a guarantee that every network filters the range correctly.
Which other special-purpose blocks does the result list?
On an exact special-purpose result, this table links every other listed special-purpose block in the same address family so the reference pages can be opened directly. The entries are not necessarily contained by, adjacent to, or otherwise related to the queried prefix.
Block
The standard range notation for another special-purpose block in the same address family.
Name
The standardized or registry-provided purpose assigned to the listed block.