Google's main ASN is AS15169. That's one Google ASN out of 21 that ARIN lists under three separate Google org IDs, and Amazon and Microsoft are built the same way: one famous number, then a long tail of ASNs split by customer type, legal entity, and acquisition.

So if you're grouping log traffic, writing a WAF rule, or deciding whether a request "came from Google," one number won't cover it, and lumping them all together is worse. This post skips the basics. For those (what an AS is, how BGP uses it, who hands them out), see this guide to autonomous system numbers .

TL;DR

AS15169 is Google's primary ASN, but it is not a reliable google-services classifier by itself. AS396982 and AS19527 are explicitly associated with Google Cloud customer traffic, but security policy should still classify the individual prefix using Google's published service, Cloud, or crawler range files.

An AS is a routing policy, not a company.…