Archive for December, 2010

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 this topic from early on in my Cisco studies. Let us review some key points regarding this metric and hopefully put some of your own misconceptions to rest.

  • While we are taught since CCNA days that the EIGRP metric consists of 5 possible components – BW, Delay, Load, Reliability, and MTU; we realize when we look at the actual formula for the metric computation, MTU is actually not part of the metric. Why have we been taught this then? Cisco indicates that MTU is used as a tie-breaker in a situation that might require it. To review the actual formula that is used to compute the metric, click here.
  • Notice from the formula that the K (constant values) impact which components of the metric are actually considered. By default K1 is set to 1 and K3 is set to 1 to ensure that Bandwidth and Delay are utilized in the calculation. If you wanted to make Bandwidth twice as significant in the calculation, you could set K1 to 2, as an example. The metric weights command is used for this manipulation. Note that it starts with a TOS parameter that should always be set to 0. Cisco never did fully implement this functionality.
  • The Bandwidth that effects the metric is taken from the bandwidth command used in interface configuration mode. Obviously, if you do not provide this value – the Cisco router will select a default based on the interface type.
  • The Delay value that effects the metric is taken from the delay command used in interface configuration mode. This value depends on the interface hardware type, e.g. it is lower for Ethernet but higher for Serial interfaces. Note how the Delay parameter allows you to influence EIGRP pathing decisions without the manipulation of the Bandwidth value. This is nice since other mechanisms could be relying heavily on the bandwidth setting, e.g. EIGRP bandwidth pacing or absolute QoS reservation values for CBWFQ.
  • The actual metric value for a prefix is derived from the SUM of the delay values in the path, and the LOWEST bandwidth value along the path. This is yet another reason to use more predictive Delay manipulations to change EIGRP path preference.

In the next post on the EIGRP metric, we will examine this at the actual command line, and discuss EIGRP load balancing options. Thanks for reading!

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Dec
28

INE is happy to announce a new class dedicated to the recently introduced Cisco Certified Design Expert (CCDE) certification. The first CCDE Practical Bootcamp is to be run on May 1-5th in Chicago, right before the actual CCDE practical exam that is scheduled on May 6th. Our goal was designing a “last-week” refresher and booster class to finalize your CCDE exam preparation. Students are assumed to have solid theoretical knowledge of the exam’s technology base prior to attending. This blog posts gives you a quick overview of the class structure and pre-requisites you should meet in order to benefit the most from this training offer.
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Dec
23

We’d like to send a huge congratulations out to Steven Glowacki who just emailed to thank us for helping him pass his CCIE Voice exam and get the newest number – 27831!

Congratulations Steven!

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Dec
21

If you have spent any time in the R&S forums in the IEOC, you have seen the username Deepak Arora. Deepak has achieved Elite status in the forum and is always challenging and helping his peers with his excellent posts.

Thank you so much Deepak, and we look forward to celebrating your number soon. We are placing 100 GradedLabs rack rental tokens in your account as a small gesture of our appreciation.

I am sure many are interested in Deepak’s story…here it is:

Deepak at a Cisco event in South Africa.

Deepak at a Cisco event in South Africa.

I started my career in mid 2003 as a System Support Engineer after passing my 3 Year regular Diploma in Electronics (Microprocessor). During the last semester of my study in college I got this opportunity in a campus interview session. Could you believe I was just a 19 year old kid at that point with no idea how things worked in the real world ?…hehe

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Dec
13

Just wanted to throw out a quick reminder to all of you involved day-to-day with Cisco Unified Communications in some fashion. Tomorrow I will host a free vSeminar on configuring and utilizing Active Directory as a source of LDAP user synchronization and authentication with the Cisco UC architecture servers.

If you still haven’t registered, you can do so right up until the webinar begins. To do so, simply click here and fill in your requested information at the bottom of the page.

In case you missed any previous vSeminars, be sure to check out the recent updates here.

Hope to see you tomorrow!

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Dec
08

This is a short publication to help you get started with Graded Labs Racks Rentals for CCIE Routing and Switching. We often see people having repeating issues when renting the rack time, so this is guide on how to avoid them. This document is a companion to the following class-on-demand videos: Using the GradedLabs.com Rack Scheduling System and Access the Racks. It is recommended that you both read this publication and watch these short videos to fully benefit from Graded Labs rack rentals.

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Dec
02

After working with the December 2010 London Bootcamp on Multicast for the better part of Day 4 in our 12-day bootcamp, I returned to the hotel to find the following post on my Facebook page – “Multicast is EVIL!”

Why do so many students feel this way about this particular technology? I think one of the biggest challenges is that troubleshooting Multicast definitely reminds us of just what an “art” solving network issues can become. And speaking of troubleshooting, in the Version 4 Routing and Switching exam, we may have to contend with fixing problems beyond the scope of our own “self-induced” variety. This is, of course, thanks to the initial 2 hour Troubleshooting section which may indeed include Multicast-related Trouble Tickets.

Your very best defense against any issues in the lab exam regarding this technology – the new 3-Day Multicast technology bootcamp. Also, be sure to enjoy the latest free vSeminar from Brian McGahan – Troubleshooting IP Multicast Routing.

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Dec
01

Catalyst switch port security is so often recommended. This is because of a couple of important points:

  • There are many attacks that are simple to carry out at Layer 2
  • There tends to be a gross lack of security at Layer 2
  • Port Security can guard against so many different types of attacks such as MAC flooding, MAC spoofing, and rouge DHCP and APs, just to name a few

I find when it comes to port security, however, many students cannot seem to remember two main points:

  1. What in the world is Sticky Learning and how does it work?
  2. What is the difference between the different violation modes and how can I remember them?

Sticky Learning

Sticky learning is a convenient way to set static MAC address mappings for MAC addresses that you allow on your network. What you do is confirm that the correct devices are connected. You then turn on sticky learning and the port security feature itself, for example:

switchport port-security maximum 2
switchport port-security mac-address sticky
switchport port-security

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