Convergence: measuring what your network actually does
Everyone claims sub-second failover. Very few have measured it.
Writing
Routing
OSPF, BGP, static and policy routing, VRFs and multicast: how routes are chosen, how they fail, and how to read what a router is actually doing.
Default routes and the black holes they create
A default route means "send it here and hope". Sometimes hope is misplaced.
VRFs: separation without separate hardware
One router, several routing tables that cannot see each other. Where that helps and what it costs.
Static routes: when they are the right answer
Dynamic routing is not automatically better. Sometimes the static route is the professional choice.
Administrative distance, explained properly
It is not a metric and it never leaves the router. That is the whole idea.
Route redistribution and the loops it creates
Two protocols feeding each other at two points will create a loop. Here is how to stop it.
BGP for people who run a single uplink
You may not need BGP. If you do, the parts that matter are few.
When OSPF neighbours will not form
The adjacency state tells you which check failed. Work the list in order.
OSPF cost and the traffic taking the wrong path
Traffic prefers a slow link over a fast one. The cause is usually a default reference bandwidth.
OSPF areas and why the design matters
Areas are not organisational tidiness. They control how much work every router has to do.