The Routing Wall of Shame
The reported culprit behind last week’s disruptions appears to be a well-known network technical risk that turned into a not-unexpected annoying problem: the global Internet routing table apparently exceeded 512,000 routes. As a result, many older routers that cannot support more than that number of routes because of memory and other limitations are at risk of sporadically causing some level of local Internet service instability until they are upgraded or replaced to handle the ever increasing number of Internet routes [pdf]. Speculation was that Tuesday’s disruptions were caused in part—or at least exacerbated—by the network activity of Verizon, which pushed the routing table to exceed the 512K threshold for a short time. The 512K mark is expected to be crossed permanently any time now, however.
Router supplier Cisco warned about a need to upgrade routers on its blog back in May when the global routing table passed 500,000 routes. It also laid out what its customer could do to upgrade their Cisco kit or perform workarounds. Last week, with the 512K milestone seemingly reached, Cisco posted another blog saying that it was really time to take action to “avoid any performance degradation, routing instability, or impact to availability.”