Hi Eric, You might want to read up on : http://labs.ripe.net/Members/erik/ripe-ncc-and-duke-university-bgp-experimen t The cisco case involved : http://www.cisco.com/en/US/products/products_security_advisory09186a0080b441 1f.shtml Short detail from the Cisco site: This vulnerability affects Cisco IOS XR devices running affected software versions and configured with the BGP routing feature. The vulnerability manifests itself when a BGP peer announces a prefix with a specific, valid but unrecognized transitive attribute. On receipt of this prefix, the Cisco IOS XR device will corrupt the attribute before sending it to the neighboring devices. Neighboring devices that receive this corrupted update may reset the BGP peering session. Could you provide insight in why you are specifically looking for a Cisco IOS bug that has taken down a network ? Regards, Erik Bais