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.