Jan
03
Continuing my review of titles from Petr’s excellent CCDE reading list for his upcoming LIVE and ONLINE CCDE Bootcamps, here are further notes to keep in mind regarding EIGRP. About the Protocol The algorithm used for this advanced Distance Vector protocol is the Diffusing Update Algorithm. As we discussed at length in this post, the metric is based upon Bandwidth and Delay values. For updates, EIGRP uses Update and Query packets that are sent to a multicast address. Split horizon and DUAL form... Read More
Jun
02
This goal of this post is brief discussion of main factors controlling fast convergence in OSPF-based networks. Network convergence is a term that is sometimes used under various interpretations. Before we discuss the optimization procedures for OSPF, we define network convergence as the process of synchronizing network forwarding tables after a topology change. Network is said to be converged when none of forwarding tables are changing for "some reasonable" amount of time. This "some" amount... Read More
May
25
It isn't my fault, they configured it that way before I got here! That was the entry level technician's story Monday morning, and he was sticking to it.  :) Here is the rest of the story.   Over the weekend, some testing had been done regarding a proposed BGP configuration.   The objective was simple, R1 and R3 needed to ping each others loobacks at 1.1.1.1 and 3.3.3.3 respectively, with those 2 networks, being carried by BGP.  R2 is performing NAT.    The topology diagram looks like this: The... Read More
Apr
06
Having a blast in Chicago with the RS bootcamp students.    Thanks for all the hard work you are doing this week! A student from a past Reno class, named Michal, asked if I would create a blog post regarding BGP proportional load balancing based on the bandwidth of the links to EBGP peers. It has been on my list of things to do, and here it is. Thanks for the request Michal. The secret to this trick is to pay attention to the links between directly connected external BGP neighbors, (in this... Read More
Aug
29
If you are interested in Part 1 of this blog series - click here. Question 2 of 105 Given the topology and configurations shown in the exhibits. Which devices will receive EIGRP Query packets if R1 loses its route information for the 10.10.10.0/24 prefix? a) None of the devices b) R2, R3, R4, R5, R6, R7 c) R2, R3, R6, R7 d) R2, R3, R4, R5 e) R2, R3 Read More
Aug
05
As a former English Major at the University of Massachusetts, Amherst, I really loved the oxymoron. You remember those..."sharply dull" or "cruel kindness". Well, the OSPF protocol has one whopper of an oxymoron in its special areas - The Totally, Not-So-Stubby area! When we last left our Area 11 in Part 4 of this blog series, it was a Not-So-Stubby Area, with the default-information-originate command used on the Area Border Router (ABR) in order to ensure a default route existed in the area.... Read More
Jul
31
Click here for Part 1 of the series or click here for Part 3 of the series. Now it is time for us to examine yet another OSPF special area type - the Not-So-Stubby Area. I am sure you recall out topology from the previous parts, but here it is again: Read More
Jul
28
Click here for Part 1. Click here for Part 2. In this part of our blog series on OSPF area types, our Area 11 is going to undergo a major flashback! The area is going to be reintroduced to an early 1980's American stereotype called Valley Girls and their Valspeak. The area is no longer going to be Stubby, but it is going to be like. . .like Totally Stubby! Lets review how we left Area 11 and how things looked when it was just a Stub area: Read More
Jul
26
Welcome back to our series on OSPF areas. Click here for Part 1 of the series. It is time to focus on normal areas and stub areas in this post. Recall our topology: Read More
Jul
25
Thanks to one of our brilliant CCIE R/S Written students, Nish, for his request of this series of INE blog posts. Nish is still struggling a bit with the different OSPF area types and how exactly they impact Link State Advertisements (LSAs). In this series, we will tackle each of the different OSPF areas in great detail, confirming our Level 1 knowledge at the command line as we progress. Here is the network we will use in this first post. Notice this simple network can be constructed easily in... Read More

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