All-in-one IPv4 / IPv6 Address Lookup

AS20001 (Charter Communications Inc) manages the 23.240.208.0/21 prefix block (approximately 2048 addresses) in the Other category. AS20001 independently controls its routing policy, peering relationships and IP allocation — Charter Communications Inc is directly responsible for traffic to and from addresses in the 23.240.208.0/21 block. The IP 23.240.209.121 resides in United States California Los Angeles (timezone America/Los_Angeles); its position within this block determines routing behavior and connectivity characteristics.

The reverse DNS record resolves to syn-023-240-209-121.res.spectrum.com, which may reflect a different service layer or hosting configuration. The mismatch between PTR and provider name may cause elevated scrutiny from mail servers and WAFs during reverse verification.

As a Home broadband address, it is part of the ISP's dynamic pool — multiple users may share the same external IP over time, and geolocation accuracy is limited to the ISP's registered region rather than the individual subscriber's location. Residential IPs carry high fraud-prevention value but low geolocation precision; prioritize behavioral signals over address reputation.

Recommendation: 23.240.209.121 is a residential IP — prioritize behavioral signals over IP reputation. Monitor for abnormal request velocity, repeated failed logins or automated patterns. Avoid blanket blocking of residential IPs even when Spamhaus lists them (PBL entries are informational, not indicative of abuse).

If you operate a website or service that receives traffic from this IP, note that the same external address may represent multiple different subscribers behind CGNAT. Blocking this IP could unintentionally exclude legitimate users — consider applying rate-limiting per session rather than per-IP.