Route Summarization
We often take network routing for granted, but in an instance, it could bring down the whole of the Internet. Along with IP, TCP, Ethernet and ARP, it was the thing that allowed the Internet to scale up. With this, I can turn my computer on, and almost instantly it can be part of the Internet and discovered if required. Without routing we would need a large database of look-up addresses, and every time you connected you would have to make sure that you had your IP and MAC address registered so that others could find you. A horrible little protocol called ARP does the magic within your local network — everything between you and the network gateway — so that you can be discovered when you are on- or off-line. But when routing goes, such as in the recent Cloudflare outage, it can have serious implications and can take out large-scale infrastructures.
So how do gateways and routers actually know how to find their way to the destination. Well, they often are configured with the places that they know about — typically the networks that they connect to, and for local traffic — and then just send anything they don’t know about to a default router, who they hope will know. And these routers, too, intercommunicate and pass on new information about networks that they have discovered, and the best way to get to them.
