TSHOOT

Whenever you are faced with troubleshooting a routing problem and the routing table looks normal, don't forget to check CEF. Cisco Express Forwarding (CEF) has been enabled by default for quite some time on most Cisco routers and has been known to cause issues from time to time.

I've created a list of a few of the most common (and a few not so common) CEF show commands that can help you track down a problem. Let's start with the basics - the FIB and the Adjacency table.

Forwarding Information Base (FIB) - This is a table that the router builds based on the routing table, but it's not the same thing as a routing table.  It contains the same forwarding decision information, but where the routing table would be like an encyclopedia of where to send packets, this is a cheat sheet.

Adjacency table - This is a table of all the layer 2, next hop information for the entries in the FIB.

If you have been thinking about going for the CCNP certification or are already working toward that goal, you have undoubtedly wondered what the TSHOOT exam has in store for you. Jeremy posted his thoughts on it after taking the exam last year. The official Cisco TSHOOT page also has specific information about the exam. However, sometimes it helps when the information is spoon fed to you in a video format. 

I stumbled on the following video and figured it was worth sharing. Not only was it informative, it reminded me of the pre-flight "fasten seatbelt" routine flight attendants go through when you travel.