Keith Bogart, CCIE #4923

Author Archives: Keith Bogart, CCIE #4923

New to the INE Course Library – Implementing Inter-VLAN Routing

This course covers the basics of implementing inter-VLAN routing by explaining the theory behind two common methodologies, as well as their implementation on Cisco routers and switches. By the end of this course students will be able to explain the differences between “Router-On-A-Stick” and “Switched Virtual Interfaces,” as well as how to implement inter-VLAN routing using either of these techniques.

Why You Should Watch:

Virtually all organizations that implement VLANs into their switched networking topologies also need to know how to route IP traffic between those VLANs. Knowing the techniques available to accomplish this kind of routing is essential whether you are managing a network, or simply pursuing a networking certification (like the Cisco CCNA).

Many learners are confused about the differences between VLANs and SVIs (Switched Virtual Interfaces) as well as their inter-relationship. This course is meant to clarify any confusion you may have between those differences, and teach you both the theory and implementation (utilizing Cisco IOS software) of Inter-VLAN Routing.

Who Should Watch:

This course is intended for anyone wanting to learn about inter-VLAN routing with an emphasis on the techniques to do so using Cisco routers and switches. A basic familiarity with the Cisco IOS command Continue reading

Understanding the EIGRP command, “metric rib-scale”


You may recall that, when using Named-Mode EIGRP configuration you have automatic access to EIGRP Wide Metrics.  In addition to providing you a new K-Value (K6 which is used against Jitter and Energy) the EIGRP Distance formula has been revised (what they call, “scaled”) to account for links above-and-beyond 10Mbps.  Remember that with Classic-Mode EIGRP, the formula looked like this:

metric = ([K1 * bandwidth + (K2 * bandwidth) / (256 - load) + K3 * delay] * [K5 / (reliability + K4)]) * 256

In the formula, the “**bandwidth**” value was represented as:

BW = 10^7 / minimum BW


The problem with this “classic” method was that any link with a bandwidth higher than 10,000,000 bps (which only equates to 10Mbps, or 10^7 bps) was given the same BW value as an Ethernet segment.  In other words, whether you put Ethernet into that formula,  FastEthernet, Gigabit Ethernet, or anything even higher…they all equate to “1″. So in Classic Mode EIGRP, EIGRP couldn’t distinguish between these types of links to develop an accurate path to a destination.

When EIGRP Wide-Metrics were developed, Cisco “scaled” some portions of the formula to account for faster links (as Continue reading

OSI Model…moving up-and-down the stack

Hello everyone!
I recently received an email from a learner who is studying for his CCNA Routing-and-Switching Certification and he had a few excellent questions about the OSI model and how, exactly data moves from one-layer to the next. I figured my response might prove valuable to others studying for their CCNA so…here it is!

  1. Learner-Question: In video of the osi model, you said that the session layer should provide the source and destination port number but the fields of those ports are at the transport header- my question is how does the session layer put this number on field which does not exist in that time (when i send the date the encapsulation process goes down from the app layer)?

    In order to thoroughly answer all of your questions below, one really needs to know about computer programming, APIs, etc…which frankly, I know very little about. But what I do know, I’ll try to explain. From my understanding, there are some kind of software “links” or “hooks” which are used to allow a program at one layer of the OSI model to communicate with a program at another layer. Many applications have software built-in that provide multi-layer functionality. Continue reading

PPP CHAP Authentication Question


The following question was recently sent to me regarding PPP and CHAP:


At the moment I only have packet tracer to practice on, and have been trying to setup CHAP over PPP.

It seems that the “PPP CHAP username xxxx” and “PPP CHAP password xxxx” commands are missing in packet tracer.

I have it set similar to this video… (you can skip the first 1 min 50 secs)

As he doesn’t use the missing commands, if that were to be done on live kit would it just use the hostname and magic number to create the hash?


Also, in bi-directional authentication, do both routers have to use the same password or can they be different as long as they match what they expect from the other router?

Thanks, Paul.


Here was my reply:

Hi Paul,

When using PPP CHAP keep in mind four fundamental things:

  1. The “magic number” that you see in PPP LCP messages has nothing to do with Authentication or CHAP.  It is simply PPPs way of trying to verify that it has a bi-directional link with a peer. When sending a PPP LCP message a random Magic Number is generated. Continue reading