OSPF: routers that find their own routes

The idea

officeRouter, coreRouter and dataCenterRouter run OSPF: the routers share a map of every link, each computes the cheapest path itself, and a laptop in the office keeps reaching the data center's web server when coreRouter fails.

Steps

1. Hello, is anyone there?

   Each OSPF router says Hello on its links every second. Listen on coreRouter, then list officeRouter's neighbours. Routers share maps only with neighbours they hear, so finding them comes first.

   coreRouter:~# timeout 3 tcpdump -nni any -v proto ospf
   officeRouter:~# vtysh

2. One map, shared by all

   Each router describes its own links and floods that to everyone. Read officeRouter's map, then dataCenterRouter's. If every router holds the same map, they all agree on the network, and their routes cannot contradict each other.

   officeRouter:~# vtysh
   dataCenterRouter:~# vtysh -c 'show ip ospf database'