Facebook Vanished From the Internet for 6 Hours. Here's How the Internet Finds Anything.

On October 4, 2021, Facebook, Instagram and WhatsApp disappeared from the internet for about six hours. Nobody hacked them. This video explains the internet's address book (DNS) and its map (BGP), the one command that cut Facebook off, why a safety feature made it worse, why the fix took six hours, and what a 2008 YouTube detour through Pakistan shows about how networks trust each other. Previous episode: How the stock market prices a company    • GameStop Went From $20 to $483 in 16 Days....   CHAPTERS 00:00 The day Facebook vanished 00:35 The address book 01:18 The map 02:05 One command 02:32 A safety feature 03:14 Six hours 03:49 Trust 04:30 How the pieces fit SOURCES Cloudflare, Understanding how Facebook disappeared from the Internet (Oct 4, 2021) https://blog.cloudflare.com/october-2... Facebook Engineering, More details about the October 4 outage (Oct 5, 2021) https://engineering.fb.com/2021/10/05... The Register, Facebook outage explained in detail (Oct 6, 2021) https://www.theregister.com/2021/10/0... Computer Weekly, Facebook unplugged for six hours due to configuration error https://computerweekly.com/news/25250... Facebook third-quarter 2021 results (SEC 8-K exhibit) https://www.sec.gov/Archives/edgar/da... Root Server Technical Operations https://www.root-servers.org Geoff Huston (APNIC), A day in the life of BGP (June 2025) https://ispcol.potaroo.net/2025-06/da... RIPE NCC, YouTube Hijacking: A RIPE NCC RIS case study https://www.ripe.net/publications/new... MANRS, What is route origin validation? https://www.manrs.org/2020/10/what-is... ABOUT THIS VIDEO "A little before noon" and "around 5:30" are New York times (Cloudflare's timeline: about 15:40 and 21:28 UTC). "About 84,000 networks" counts the network numbers in the global routing table; one organization can run several. DNS lookups are simplified: resolvers usually answer from a cache, and the chain runs root, then the top-level domain, then the company's own servers. Facebook's DNS servers kept running; they withdrew their route announcements, so nobody could reach them. The IP address shown is an illustrative documentation address. The network maps are schematic. Pakistan Telecom's intent (a domestic YouTube block) is from press reports; the routing events are from RIPE NCC. Spotted an error? Say so in the comments and it will be corrected here.