What is an ASN?
An Autonomous System Number identifies a network (an ISP, a cloud provider, a large enterprise) that has its own routing policy on the public internet. ASNs are how BGP — the protocol that holds the internet together — knows which network owns which range of IP addresses. AS4158 is the ASN assigned to CITYUNI-AS-AP City University of Hong Kong.
If you want to know which ASN your connection is on, visit the home page — your ASN is shown alongside your public IP.
Data source
This page is generated server-side from RIPE Stat (free, public, no API key). Holder names, country codes, and announced prefixes come directly from RIPE's BGP table view. Cached for one hour at the edge.