Posts Tagged ‘ACL’


Answers for Part II

So the answers to the exciting tasks at hand….

There was a good amount of activity surrounding answers submitted for the contest!  It was good to see that many people interested in them!  Now, it’s time to go through the answers and stretch the imagination a bit!  Be prepared for some stretching as well!

One quick thing to point out before we get started, there was a question asked about why /24 routes won’t have a “.255″ as the fourth octet.  This really depends on how we are using the ACL.  If we are doing traffic filtering, where packets will obviously come from hosts INSIDE the /24, then yes, I’d use a “.255″ mask.

However, when the entry is being used for a routing filter, and it’s a /24 route…  The fourth octet will, by definition, always be “.0″ and shouldn’t be changed.  So the mask of “.0″ prevents anything from changing!

Now…  On to the answers!

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I know, I know…  I promised this a while back, after I did the first part.  Sorry ’bout that!

So we’ve played around a bit with the access-list idea and some binary matching.  So let’s expand our brains even further!

I will start out by telling everyone that I am NOT picking on or otherwise attempting to insult any CCNA’s out there by comparing methodology to what is learned in CCNA.  The idea being that there are basic and advanced ways to learn things.

When we all first learned fractions, if anyone attempted to explain more advanced methods of long division, or finite state mathematics, or anything we now consider to be “basic algebra”, plain and simple….  our brains would have imploded!  It wouldn’t have been pretty at all.

There is a time and a place for everything.  When first beginning as a CCNA, the concept of “network” and “network mask” and wonderful subnets on standard bit-boundaries is good.  It’s a starting point.  Just realize that it isn’t the end point, and as CCIE Candidates, we need to see beyond those initial learning steps in order to succeed!  If you have stumbled across these blogs, and are still a CCNA, my sincere apologies as I did not mean to offend!  (And my apologies for any induced-brain-implosions!)

Now, all those legal disclaimers aside, it’s time to move up a notch in Binary Math.  We’re still counting to one, we’re just doing it with more finesse now!  So let’s start with our first problem for Part II.

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