OnLAMP.com Publishes Good Description of SQL Slammer Impact on Some Cisco Routers
An article by Iljitsch van Beijnum on OnLAMP.com called Network Impact of the MS SQL Worm does a great job of explaining the impact of the SQL Slammer worm on three networks with different Cisco routers.
In van Beijnum's experience, some Cisco routers lost their Border Gateway Protocol (BGP) sessions. When that occurred "the router was unable to advertise the network's IP address ranges to the rest of the world, with the result that these addresses became unreachable." This was compounded by problems with the Cisco Express Forwarding (CEF) algorithm on routers that did not have enough memory. Consequently, the author recommends that packet forwarding algorithms be studied from a worst-case perspective.
Van Beijnum also gives documents some of the steps he took to log and, later, filter the network traffic generated by the worm. So, the article gives insight into how an experienced network manager researches and solves network problems as they occur.