May
10
Edit: Thanks for playing! You can find the official answer and explanation here. Read More
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
Dec
30
To start my reading from Petr's excellent CCDE reading list for his upcoming LIVE and ONLINE CCDE Bootcamps, I decided to start with: EIGRP for IP: Basic Operation and Configuration by Russ White and Alvaro Retana I was able to grab an Amazon Kindle version for about $9, and EIGRP has always been one of my favorite protocols. The text dives right in to none other than the composite metric of EIGRP and it brought a smile to my face as I thought about all of the misconceptions I had regarding... Read More
May
03
The purpose of event dampening is reducing the effect of oscillations on routing systems. In general, periodic process that affect the routing system as a whole should have the period no shorter than the system convergence time (relaxation time). Otherwise, the system will never stabilize and will be constantly updating its state. In reality, complex system have multiple periodic processes running at the same time, which results is in harmonic process interference and complex process spectrum.... Read More
Jan
01
In this blog post we are going to discuss some OSPF features related to convergence and scalability. Specifically, we are going to discuss Incremental SPF (iSPF), LSA group pacing, and LSA generation/SPF throttling. Before we begin, let's define convergence as the process of restoring the stable view of network after a change, and scalability as the property of the routing protocol to remain stable and well-behaving as the network grows. In general, these two properties are reciprocal, i.e.... Read More
Sep
17
This is the follow up discussion for the post titled, "Have you seen my Router ID?" The underlying issue here was trying to get OSPF to bypass the usual selection process for Router ID. The normal selection order is: Manual router ID configured under ospf process Highest IP address of a loopback in the up state in the respective routing table Highest IP address of an interface of an up state in the respective routing table If there are no up interfaces and you have not manually configured a... Read More
Sep
17
In yesterday's post, titled "Have you seen my Router ID?", a challenge section was provided. This post will focus on scrutinizing the section itself, from a strategy / analysis point of view. From a high level overview, we have two devices peering OSPF over a FastEthernet link, with some loopback networks advertised by one side, and received on the other router.  If that was all that the section was asking for, then it should be a task that anyone at CCNA level could complete.  When looking at... Read More
Sep
16
There is more than one possible solution for this challenge. Feel free to post your proposed answer in the comments section. We will try to keep comments hidden from public view, so that the fun isn't spoiled for others. Also, don't feel bad if the answer(s) aren't immediately apparent. A number of very bright people have been puzzled by this scenario.  Answers will be posted on Friday, September 18th. Read More

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