Prefix Notation

Posted On 2011-02-20 by FortyPoundHead
Tags: Networking Cisco Tutorial 
Views: 628

When you're preparing to pass the CCNA exam and earn this coveted Cisco certification, you've got to be totally prepared for the many kinds of binary and subnetting questions Cisco may throw at you.

You also have to be familiar with the different manners in which a subnet mask can be expressed, as in the following:

Believe it or not, those two values are exactly the same. The first mask is written out in the more familiar dotted decimal format, and you know by looking at those first three octets that every bit is set to "1", since the maximum value of such an octet is 255.

The second value represents the exact same mask, only this value is expressed in prefix notation. This particular value would be pronounced "slash twenty-four", and the 24 represents the number of consecutive ones that are set in the subnet mask.

Those of us who hate to type numbers are particularly appreciative of this, since it means you'll have to type a lot less numbers to represent a subnet mask. In addition, it's a lot easier to discuss masks in prefix notation than dotted decimal. ("I thought about using a two-fifty-five two-fifty-five two-fifty-five zero mask ,but then decided to use a two-fifty-five two-fifty-five two-fifty-five one-twenty-eight mask...")

Be sure you're comfortable with prefix notation before taking your CCNA exam. As with Cisco documentation, you'll most likely see masks expressed in both dotted decimal and prefix notation, and you've got to be ready to use the both as well!

About the Author

FortyPoundHead has posted a total of 1974 articles.


Comments On This Post

No comments on this post yet!

Do you have a thought relating to this post? You can post your comment here. If you have an unrelated question, you can use the Q&A section to ask it.

Or you can drop a note to the administrators if you're not sure where you should post.

Your IP address is:

Before you can post, you need to prove you are human. If you log in, this test goes away.

Beat With A Stick List Returns: By request, BWASL has returned to the site. Free your rage by telling the world about something that really grinds your gears. Add your beating.

Recent Forum Posts

BWASL returns
dwirch posted on May 13, 2017 at about 15:24 in Site News

BWASL returns
dwirch posted on May 13, 2017 at about 8:46 in Site News

Job Spammer: Balashankar Bose Bose
dwirch posted on May 11, 2017 at about 10:05 in Spammers

Job Spammer: Bharti Jigyasi
dwirch posted on May 11, 2017 at about 7:58 in Spammers

List of Shady Characters
dwirch posted on April 25, 2017 at about 16:39 in Webmaster Stuff

Job Spammer: Bilal Uddin
dwirch posted on April 25, 2017 at about 11:00 in Spammers