Indian ISP’s routing hiccup briefly takes Google down worldwide

For a short time today, people all over the world trying to access Google services were cut off because of what Dyn Research Director of Internet Analysis Doug Madory identified as a "routing leak" from an Indian broadband Internet provider. The leak is similar to a 2012 incident caused by an Indonesian ISP, which took Google offline for 30 minutes worldwide.

Routing leaks occur when a network provider broadcasts all or part of its internal routing table to one or more peered networks via the Border Gateway Protocol, causing network traffic to be routed incorrectly. In this case, the Indian ISP Hathway's boundary router incorrectly announced routing data for over 300 network prefixes belonging to Google to the Internet backbone via its provider Bharti Airtel. "Bharti in turn announced these routes to the rest of the world," Madory wrote in a Dyn Research blog entry posted this morning, "and a number of ISPs accepted these routes."

In the US, Cogent and Level 3 accepted the routes; a number of overseas carriers, including Orange, were also affected.

Hathway had its own routes to Google because the company peers with Google to provide better speed to Google's cloud, directing traffic to the closest Google data centers. That peering is a private network connection. As a result, when the routing table was accidentally broadcast to the world instead of just to Hathway's customers, much of the world was trying to access Google via Mumbai, through Hathway, instead of over the public Internet.