We're Sorry, Full Content Access is for Members Only...

If you like to keep on reading, Become a Member Now! Here is Why:

  • Learn any CCNA, CCNP and CCIE R&S Topic. Explained As Simple As Possible.
  • Try for Just $1. The Best Dollar You've Ever Spent on Your Cisco Career!
  • Full Access to our 568 Lessons. More Lessons Added Every Week!
  • Content created by Rene Molenaar (CCIE #41726)

 

323 New Members signed up the last 30 days!

satisfaction-guaranteed

100% Satisfaction Guaranteed!
You may cancel your monthly membership at any time.
No Questions Asked!


Forum Replies

  1. James,
    Only the first four bits (3 really, since E class isn't used) in the first octet determine class (as shown in the table below). You are correct in your example about 171.15.85.0/24.

    Keep in mind, however, that "class" doesn't really mean anything anymore. This is an outdated term that nobody really uses now. Even Cisco has stopped bothering to test on it!

    Binary (first 4 bits) Class
    0000                   A
    1000                   B
    1100                   C
    1110                   D
    1111                   E
  2. Hi Rene,

    What do you mean by CIDR & VLSM ? The both are same or what is the difference between them.

    Br
    Zaman

  3. andrew says:

    Zaman,
    These can be easily confused--in fact I had to review them myself to make sure I am giving you accurate information.

    VLSM is aptly named, because it means using a subnet mask of variable lengths throughout your organization with the same network block. For example, suppose your ISP has given you 10.10.10.0/24 as an IP range. Without VLSM, you would have to pick a certain subnet mask, say, 255.255.255.240 (/28) and stick with that. So if you wanted to use this block throughout your company, you would always have to use /28. This becomes wasteful in the case where you have a subnet with just two hosts, or it becomes inadequate where you have a subnet with 50 hosts. With VSLM, you have the freedom to change your subnet mask as needed, so in the case of a subnet with two hosts, you could use 10.10.10.248/30, for example, and with a subnet having 50 hosts, you could use 10.10.10.0/26, for example.

    CIDR is basically "supernetting." This is where you can aggregate networks together into larger networks beyond their natural network boundary. For example, suppose I have 192.168.0.0/24 and 192.168.1.0/24. These networks have a natural /24 boundary (because they are class C addresses), but I can using CIDR aggregate them via 192.168.0.0/23

  4. Thanks Andrew...,

3 more replies! Ask a question or join the discussion by visiting our Community Forum