Sunday, November 1, 2009

IPv6 Static Routing

In this hands-on exercise, we configure IPv6 addresses on 3 routers in a triangle. Then we configure IPv6 static routes to allow the 6 IPv6 subnets (3 loopback, 3 P2P links) to be accessible on all 3 routers.
Static routes are easy to understand. At first glance they appear simple. You just manually configure which next-hop to go to for each subnet destination. But in actual use they are very complex. In our example with 3 routers and 6 subnets, we end up using 12 static route commands to implement our routing. Even then we do not achieve full redundancy, because static routes do not reroute around network failures. Even a small production network with approximately 20 routers would have too many static route commands necessary to make a static-route implementation feasible. In the real world, using dynamic routing protocols to minimize manual configurations (minimizing both effort and errors) is necessary to achieve a robust environment.
That said, static routes are sometimes useful at the edge of your network. You redistribute static routes into your routing protocol at the edge of your network where you don't want to dynamically route with routers outside your administrative control. The goal there is just to use the static route to inject a route into your routing protocol. Not to use the static route as your primary routing mechanism.