Did you know? · No. 04 · Fun fact ·
A backbone mistake made Facebook’s DNS disappear for 5 hours 30 minutes
On October 4, 2021, a routine maintenance command unintentionally disconnected Facebook’s global backbone, the network joining its data centers. Because the DNS servers could no longer reach those centers, they withdrew the BGP advertisements that told the internet how to reach them. Facebook, Instagram and WhatsApp became unreachable.
Cloudflare observed facebook.com DNS become unavailable around 15:50 UTC and return at 21:20 UTC: five hours and 30 minutes. Recovery was harder because Facebook’s normal and out-of-band network access was down, so engineers had to follow secure physical-access procedures at data centers. For a smaller site, the lesson is not scale; it is avoiding one broken dependency that blocks both visitors and your recovery path.
Try this on your site
List how you would reach your DNS provider, host and domain registrar if your website and primary network were unavailable. Make sure at least one recovery path and emergency contact method does not depend on the systems it supports.
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