Trouble resolving ISP details via ASN lookups?

You mentioned hitting a 'snag' with ASN resolution, and honestly, calling it a 'snag' might be an understatement for the headache inconsistent WHOIS data can cause!

1. Leverage RIR APIs Directly: Instead of just relying on a generic `whois` client, consider integrating directly with the RIR APIs (ARIN, RIPE, APNIC, LACNIC, AFRINIC). Each RIR manages specific IP address blocks and their respective WHOIS data. Their APIs often provide more structured and consistent data than raw `whois` queries, allowing you to parse specific fields more reliably. You'll need to determine which RIR owns the IP block first, then query that specific RIR's service.
2. Utilize Commercial IP Intelligence APIs: For higher accuracy and less parsing overhead, specialized IP intelligence services are often the way to go. They aggregate and clean data from multiple sources, including RIRs, BGP routing tables, and their own network probes, to provide enriched `network intelligence` details like ISP, organization, and connection type.
   • Good options include MaxMind GeoIP2, IPinfo.io, and DB-IP. These provide APIs that return clean JSON data, making parsing ISP names significantly easier and more reliable than scraping raw WHOIS output.
   • While these are excellent, you could also look at alternatives like Neustar IP Intelligence or Digital Element's NetAcuity for enterprise-grade solutions.
3. Implement Multi-Source Parsing with Fallbacks: If you're committed to parsing `whois` data yourself, you need a more sophisticated parser.
   • Prioritize Fields: Look for fields like `OrgName`, `descr`, `organisation`, `netname`. Prioritize them based on common reliability.
   • Regex & Heuristics: Develop robust regular expressions and heuristics to extract common patterns. For truncated fields, sometimes the `OrgId` or `netname` can provide a unique identifier that you can then cross-reference with a known list of ISPs.
   • Multiple WHOIS Servers: Don't just query a generic `whois` server. Determine the appropriate RIR for the IP and query its specific WHOIS server (e.g., `whois.arin.net`, `whois.ripe.net`). Each RIR has slightly different output formats, so your parser will need to handle these variations.
   • Data Cleaning: After extraction, clean the data. Remove common suffixes like "LLC", "Inc.", "Network", "ISP", "AS", etc., to normalize the ISP name.
4. Cache Results: To reduce API calls and speed up lookups, implement a local cache for IP-to-ISP mappings. This is especially useful for frequently queried IP ranges.

You really hit on something with the idea of using commercial IP intelligence APIs as a primary source. That makes a lot of sense for reliability, almost like investing in a better data pipeline for this kind of data.