From the Onion, in 2007:
[…] SuproNet, a local Czech provider, single-handedly caused a global Internet meltdown for upwards of an hour today.
So what happened? How did a little Czech ISP manage to blow up the Internet?
The long answer is here, at Renesys’s blog (they’re a big internet-services company, so they know what they’re on about).
The short answer:
SuproNet were using a funny Latvian brand of router (the computers that direct traffic on the internet). They made one little screwup in their configuration, and accidentally sent out an extremely long AS-path (the “traffic directions” for how to route traffic to SuproNet).
The problem is, nobody had ever done this before – or thought it would happen. And there turned out to be a bug in the software for Cisco routers – by far the most popular routers on the ‘net – that caused them to drop connections if they ever received a long AS-path, just like the ones SuproNet was sending out.
So the bug in an obscure Latvian router triggered the bug in the world’s most popular routers – and suddenly most of Europe and most of America fell off the Internet.
But the best bit is this comment from Arbor Networks’s blog:
I have contacted the ISP here in Czech republic (Sloane). They said: “Oh that thing from yesterday? It was just a tiny little bug…” :-(