Will This Be On The Turing Test?: Understanding Routing (especially EIGRP and OSPF for CCNA)

When I did a google search on "eigrp manual summarization" (without the quotes) the very first hit was a page at cisco.com:
http://www.cisco.com/en/US/tech/tk365/technologies_white_paper09186a0080094cb7.shtml (Document ID: 16406). I found this doc to be very helpful, although to be honest it could use some serious editing (for example it wastes a significant amount of time and space talking about "output interpreter").

Original image by Fermín Galán and David Fernández:
http://neweb.dit.upm.es/vnumlwiki/index.php/Example-OSPF_1.8

Another document that is really nice at explaining the routing process in Cisco IOS is: Route Selection in Cisco Routers (Document ID: 8651). This one is short and sweet and anyone who wants to learn more about the fundamentals of Cisco IOS should sit down and read it straight through.

For an excellent (and "as simple as possible but no simpler") discussion of the Shortest Path First algorithm, see Computer Networking: A Top-Down Approach, 6E, by Kurose and Ross, especially Chapter 4, Section 5: Routing Alforithms. Personally I didn't think their treatment of Distance Vector was as good, but their whole chapter on routing (chapter 4) is something I want to get back to and read through carefully from beginning to end.

Radia Perlman's discussion of both Link-State and Shortest Path First is very good in her classic Interconnections. If you don't know about Perlman, she invented Spanning Tree Protocol and also IS-IS routing protocol, so she's kind of a big deal.

I am really liking the CCNP "self-study" book on routing by Catherine Paquet and Diane Teare. I'm studying the CCNA curriculum right now, but everytime you get get to the good stuff you read "this topic is discussed in CCNP." I think that Paquet and Teare's book is good for someone working on CCNA who plans to move directly to CCNP! The full title of the book is Building Scalable Cisco Internetworks, 3e.

Here is an excellent summary of the query process in EIGRP (taken from here: http://www.ccie.net/blogs/eigrpquery-process):

Query process happens with the following:
1.Query is sent when route is lost and NO Feasible Successor is available.
2.The Lost Route is now in active state.
3.Query then sent to all neighboring router on all interface EXCEPT the interface to successor.
4.If the neighbors don't have lost route information, queries are sent to their neighbor.
5.If the router has a alternate route, it answers the query and stop query propagation.

And here is a more in-depth discussion, by Jeremy Stretch of PacketLife.Net, of the EIGRP Query process, which nicely explains, among other things, why EIGRP really is a true Distance Vector protocol and NOT some kind of "hybrid":
Understanding EIGRP Queries.

Finally, here are some key concepts that I consider "key" not because of their role in routing so much as their role in making sure that you understanding routing:

route summarization
the difference between routing and forwarding
this sentence: "The longest prefix match always wins among the routes actually installed in the routing table, while the routing protocol with the lowest administrative distance always wins when installing routes into the routing table."
level one versus level two routes, parent and child routes, ultimate routes
what the prefixes in level one routes mean; when the classful mask is used as opposed to when the subnet mask is used; and how to interpret the output of "sh ip route" in general.
know why it is almost always a good idea to turn off classful automatic summarization ("no auto").
know what this sentence means (referring to EIGP): "Queries result in a split horizon only when a router receives a query or update from the successor it is using for the destination in the query."

Here are the short and the long forms of the EIGRP metric: