Re: [nznog] Interesting - How a Router's Missed Range Check Nearly Crashed the Internet

On 22 Feb 2009, at 17:00, Skeeve Stevens wrote:

Is this just the 4byte ASN thing from months ago or something new?

Something very different, the 4-byte ASN thing was caused by AS_CONFED_SETs existing in the AS4_PATH attribute, where they are illegal, and the compatibility mode of the AS4 system allowing this to propagate unchecked. A group of us are trying to fix the RFC on the idr(a)ietf list, proposing that if BGP speakers encounter this, they ignore the illegal UPDATE (or treat as WITHDRAW if the prefix is already installed into the RIB). http://www.andyd.net/media/talks/asn4_breaks_network.pdf for my slides where I presented this at nanog. Andy