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.
Platform
Cisco IOS / IOS-XE
Cisco routers and switches running IOS or IOS-XE. Much of it carries to NX-OS.
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.
Interface counters and what they actually tell you
Every error counter has a specific meaning. Knowing which is which turns guessing into diagnosis.
Cable faults that look like software faults
Hours get spent in configuration for problems that live in the first metre of the path.
Three questions before touching a production network
Not process for its own sake. Three questions that have prevented more outages than any tool.
Jumbo frames: worth it, or not
They help in specific places and cause silent breakage everywhere else. Decide deliberately.
The difference between a slow network and a busy one
Both feel identical to users. They have different causes and different fixes.