Wrong answer or just confusion?

jscimeca715

Hello all, I'm studying Wendall Odom's book in preparation for INCD1 and have a question. He states that the total number of networks for class a is 2^7-2. Class B 2^14 and Class C 2^21. I was wondering why it wouldn't be raised to the power of 8, 16, and 24 respectively? I think I'm just having a moment where I don't understand so any help would be appreciated.

pooker

Because he is talking about the number of networks , the smallest network you can have would have one ip address, which would never work but he is just showing for example. 2^7 = 128, - 2 = 126 if you had the command no ip subnet zero entered. If your talking about total number of hosts it would be 2^8 - 2, I think its bacwards though because a class c would have 2^7 and so on

the minimum bit you could borrow would be 1 , which would make the networks look like this

192.168.2.0
192.168.2.2
192.168.2.4


he is just telling you the maximum networks supported by that class

jscimeca715

Pooker: Do you have Wendall Odom's ICND1 book? I'm referring to the table on page 110 (Table 5-5) column four. I'm still not clear as to why this is the case, no offense, maybe I'm overthinking it?

dynamik

That's just how the number of networks in Class A, B, and C are represented mathematically. For example, if you used all 8 bits for a Class A, there would be nothing left for the other classes.

redgren

jscimeca715 wrote:

Hello all, I'm studying Wendall Odom's book in preparation for INCD1 and have a question. He states that the total number of networks for class a is 2^7-2. Class B 2^14 and Class C 2^21. I was wondering why it wouldn't be raised to the power of 8, 16, and 24 respectively? I think I'm just having a moment where I don't understand so any help would be appreciated.

I think in that table he is removing the reserved addresses, so what he is giving you is the # of available network numbers.