ASN Overview
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Field Value Copy
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Prefix IP Version Copy
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ASN Name Type Copy
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                            Tags:
                                                            
                                    Diagnostics
                                
                                ,                                                             
                                    IP Addressing
                                
                                ,                                                             
                                    Networking
                                
                                                                                    

                        

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Autonomous System Numbers are numeric identifiers for networks that control routing on the public internet and they indicate who operates a block of addresses and where responsibility sits. With ASN owner and prefix lookup, you can connect a number or an IP to the organization behind it and see scope at a glance.


  
Engineers use these identifiers to understand reachability and make peering choices, and analysts use them to trace responsibility during investigations or troubleshooting. You enter an ASN or an IP and you get the holder, country, status, announced prefixes, counts by IP version, peer counts, neighbor names, and registry contacts so you can act quickly.


  
A realistic way to read results is to note the total prefixes, the mix of IPv4 and IPv6, and the shortest and longest prefix lengths since these hint at aggregation and footprint. A brief look at upstream and downstream counts shows connectivity posture, and named neighbors provide a fast cross check across providers.


  
Registry data can be incomplete or slow to change so always corroborate important decisions with multiple sources. For consistent comparisons, repeat lookups the same way and record the timestamp that the registries report for last update.






  
Technical Details:


  
The input is either an Autonomous System Number (ASN) or an IP address. For an IP address, the origin ASN is resolved first; for an ASN, a normalized numeric form is taken as the key. The tool then assembles registration facts, currently announced prefixes, neighbor relationships, and public contact roles from common Internet registries.


  
From the announced prefix list, several summary quantities are computed: total prefixes, counts by IP version, and the shortest and longest prefix lengths. Counts of neighbor types are also computed. These help characterize footprint and upstream versus downstream exposure without requiring raw table inspection.


  
Results should be compared across time windows rather than across unrelated networks. Registry and measurement backends update on their own cadences, so values near a change boundary can shift between runs.


  
Processing pipeline

  
    
    
  1. Trim input; if multiple lines exist, keep the first and record extra lines.
    2. 
    
  2. Detect IP literal; if IP, resolve origin ASN using a connectivity service.
    3. 
    
  3. If not IP, normalize ASN by removing a leading “AS” and validating digits.
    4. 
    
  4. Query routing statistics for overview, announced prefixes, peer counts, and neighbors.
    5. 
    
  5. Compute prefix statistics: totals, IPv4 and IPv6 counts, shortest and longest lengths.
    6. 
    
  6. Fetch registration data via RDAP; take the first registry that returns usable data.
    7. 
    
  7. Augment with public metadata from widely used ASN datasets where available.
    8. 
    
  8. Render Info, Prefixes, Peers, and JSON views; enable CSV and JSON copy or download.
    9. 
  


  

    
      
        
          p≔list of announced prefixes
        
        
          ptotal=|p|
        
        
          pv4=count(ip_version∈{“4”, “IPv4”})
        
        
          pv6=count(ip_version∈{“6”, “IPv6”})
        
        
          ℓmin=min( CIDR length of each prefix in p )
        
        
          ℓmax=max( CIDR length of each prefix in p )
        
      
    
  


  

    

      
      
        

          Symbol
          Meaning
          Unit/Datatype
          Source
        

      
      
        

          ASN
          Autonomous System Number
          integer (1–10 digits)
          Input/derived
        

        

          ptotal
          Total announced prefixes
          count
          Derived
        

        

          pv4, pv6
          Prefix counts by IP version
          count
          Derived
        

        

          ℓmin, ℓmax
          Shortest and longest prefix length
          bits (/n)
          Derived
        

      
    

  


  

    Worked example. Prefix list:
    192.0.2.0/24 (IPv4), 2001:db8::/32 (IPv6), 198.51.100.0/25 (IPv4).
    Then ptotal=3, pv4=2, pv6=1, ℓmin=24, ℓmax=32. A shorter length indicates a broader aggregate; longer suggests more specificity.
  


  

    

      
      
        

          Field
          Type
          Min
          Max
          Step/Pattern
          Error Text
          Placeholder
        

      
      
        

          ASN or IP
          text
          —
          —
          IPv4 dotted‑decimal check; IPv6 hextet check or :: present; ASN digits after optional “AS”.
          Enter an ASN or IP address.
          AS15169 or 8.8.8.8
        

        

          Limit prefixes
          number
          0
          —
          step 1; 0 shows all
          —
          —
        

        

          Prefix sort
          select
          —
          —
          “” (source order), “length”, “alpha”
          —
          —
        

        

          Peer type
          select
          —
          —
          “” (all), “left”, “right”, “uncertain”
          —
          —
        

      
    

  


  

    IPv4 regex: ^(25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)\.(25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)\.(25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)\.(25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)$

    IPv6 regex: ^(([0-9A-Fa-f]{1,4}:){1,7}[0-9A-Fa-f]{1,4}|(([0-9A-Fa-f]{1,4}:){1,7}:)|(::([0-9A-Fa-f]{1,4}:){0,6}[0-9A-Fa-f]{1,4}))$ or s contains “::”
  


  

    

      
      
        

          Input
          Accepted Families
          Output
          Encoding/Precision
          Rounding
        

      
      
        

          Single text value
          ASN with optional “AS” prefix; IPv4 or IPv6 literal
          Tables, badges, JSON, CSV
          JSON pretty print (2 spaces); CSV with header row
          Not applicable
        

      
    

  


  
Networking & storage behavior. Requests are issued from the page to a CORS proxy, which forwards to public services: an IP‑to‑ASN resolver, RIPE routing statistics, RDAP registries, a public ASN metadata API, and PeeringDB. A 9 s timeout is applied per proxied request. No browser storage is used beyond the page context.


  
Performance & complexity. Remote lookups are batched where possible; local aggregation is linear in the number of prefixes and peers. Copy and download actions operate on in‑memory data.


  
Diagnostics & determinism. Identical inputs produce consistent processing, but returned facts can change as upstream registries update. Errors surface as inline alerts with a retry option.


  
Security considerations. Inputs are sanitized to simple patterns before querying. JSON is highlighted for display using preformatted markup. Treat third‑party descriptions and contact fields as untrusted text in any downstream use.


  
Privacy & compliance. Queries and ASN/IP values are sent to third‑party services through a proxy; outputs contain public network data. Avoid entering confidential information not required for a lookup.






  
Assumptions & Limitations:

  
    
    
  • Only the first non‑empty input line is processed in single‑item mode; extra lines are ignored.
    • 
    
  • IPv6 detection accepts compressed forms; a bare “::” triggers IPv6 detection.
    • 
    
  • Normalization removes a leading “AS” and accepts up to 10 digits for ASN.
    • 
    
  • RDAP uses the first registry that returns usable data; others are not queried thereafter.
    • 
    
  • Public metadata sources can disagree; names and contacts may vary across datasets.
    • 
    
  • Peer counts are taken from reported measurements and may reflect only selected vantage points.
    • 
    
  • Prefix statistics rely on present‑tense announcements; historical states are not included.
    • 
    
  • Sorting and limits change only the view; source order is preserved when no sort is chosen.
    • 
    
  • Heads‑up Very long or malformed lines are rejected with a generic failure message.
    • 
    
  • Heads‑up Contact fields can be empty even for valid ASNs.
    • 
  






  
Edge Cases & Error Sources:

  
    
    
  • Non‑ASCII characters in input.
    • 
    
  • Private or unrouted IP addresses that lack an origin ASN.
    • 
    
  • IPv6 unusual compressions that pass loose checks but fail upstream resolution.
    • 
    
  • Network timeouts or aborts from the proxy.
    • 
    
  • Upstream JSON schema changes or empty data sections.
    • 
    
  • Duplicate prefixes or neighbors in source data.
    • 
    
  • Trailing comments pasted with the input token.
    • 
    
  • Clock skew between “first seen” and “last updated” across sources.
    • 
    
  • Temporary registry outages that yield partial views.
    • 
    
  • Source order assumptions when mixing sorts and limits.
    • 
  

  





  
How‑to · Step‑by‑Step Guide:

  
ASN and IP lookups return holder details, announced prefixes, peers, and contacts for quick routing context.

  
    
    
  1. Enter ASN or IP in the input field.
    2. 
    
  2. Press Enter or select the lookup action to fetch data.
    3. 
    
  3. Review the overview first; note holder, country, and status.
    4. 
    
  4. Open Prefixes to scan coverage; sort by length for aggregation clues.
    5. 
    
  5. Open Peers and filter by Peer type to focus relationships.
    6. 
    
  6. Copy or download CSV/JSON if you need a portable snapshot.
    7. 
  

  
Example: Input AS64500 returns a summary plus tables; applying a prefix limit shows a concise view.

  
    
    
  • Pro tip: capture last‑updated timestamps alongside results for reliable comparisons.
    • 
  






  
FAQ:


  

    Is my data stored?
    
Lookups are sent to third‑party registries through a proxy and rendered in the page. The fragment itself does not persist inputs in browser storage.

    Avoid including confidential text not needed for a lookup.
  


  

    How accurate are the results?
    
Accuracy depends on the registries and measurement feeds at request time. Holder names and peers can change; verify critical decisions across sources.

  


  

    What units or formats are used?
    
ASNs are integers; prefixes are CIDR notated; counts are integers. JSON is pretty printed; CSV includes a header row.

  


  

    Can I use it offline?
    
No. Network requests to public services are required for every lookup.

  


  

    What does the peer type mean?
    
The type label comes directly from the neighbor dataset. Values such as “left”, “right”, or “uncertain” are passed through as reported.

  


  

    How do I find the ASN for an IP?
    
Enter the IP address. The tool resolves its origin ASN, then fetches routing and registration facts for that ASN.

  


  

    What does a very short prefix tell me?
    
Shorter prefix lengths indicate broader aggregates. Combine this with counts and peers to understand footprint versus specificity.

  


  

    Is there any cost or license noted here?
    
The fragment documents behavior only. Availability and licensing of the surrounding site are outside this scope.

  






  
Advanced Tips:

  
    
    
  •  Sort prefixes by length to scan aggregation before drilling into values.
    • 
    
  •  Filter peers by type to isolate likely providers or customers faster.
    • 
    
  •  Capture both first‑seen and last‑updated timestamps for trend notes.
    • 
    
  •  Keep a small notebook of expected neighbors for your region as a sanity check.
    • 
    
  •  Export JSON when you need to preserve the exact payload for audits.
    • 
    
  •  Re‑run lookups after planned maintenance windows to catch fresh allocations.
    • 
  






  
Glossary:

  

    
Autonomous System (AS)

    
A network under a single routing policy.


    
ASN

    
Numeric identifier assigned to an AS.


    
CIDR prefix

    
Address block written as network/length.


    
Prefix length

    
Number of significant bits in the mask.


    
RDAP

    
Registration Data Access Protocol for queryable records.


    
Looking glass

    
Public interface for route or BGP queries.