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CCNA Class

A

AndrewK78

Weaksauce
Joined
Apr 26, 2005
Messages
109
I am not wanting someone to do my work for me. For the life of me I cannot wrap my head around this. I've been at it for a few hours and have a splitting headache now. If someone would help me I would love it.

Example:

162.242.93.107/29

Find

Network Address
Broadcast Address
First usable host
Last usable host

Basically as far as I can get is breaking it down to binary which would be.

10100010 11110010 01011101 01101011

Could someone help me out and show me step by step how to get the answers and why they are the answers.


Thanks a ton
 
10100010 11110010 01011101 01101011 ip address
11111111 11111111 11111111 11111000 subnet mask (29 1 bits)

NNNNNN NNNNNNN NNNNNNN NNNNNHHH

network address is all 0's in the hosts portion
10100010 11110010 01011101 01101000

first usable subnet would be if you used 001 in the in the hosts portion
10100010 11110010 01011101 01101001

bcast is all 1's in the host portion
10100010 11110010 01011101 01101111

last usable host is 1 down from the broadcast.
 
Get the CBTNugget videos and watch the subnetting stuff. Or find some classes online.

Once you find the right explanation you will just "get it".
 
thanks for the attempt, i'll just go back at it again all of my stuff is online and the instruction isnt that good
 
Transposing the bits would technically be the right way to do subnetting, but learn block notation, it's much easier and faster.
 
I would pay someone to mentor me in subnetting, I understand converting binary back and forth but when it gets further for some reason everything doesnt click with me and I dont remember what goes where etc.
 
AndrewK78 said:
I am not wanting someone to do my work for me. For the life of me I cannot wrap my head around this. I've been at it for a few hours and have a splitting headache now. If someone would help me I would love it.

Example:

162.242.93.107/29

Find

Network Address 162.242.93.104
Broadcast Address 162.242.93.111
First usable host 162.242.93.105
Last usable host 162.242.93.110

subnet is 255.255.255.248
Click to expand...
 
Quite honestly, sir. Take the time to watch this video series. I am in high school and used these to teach myself after they were recommended by people on these forums. Six of my classmates became extremely adept as well after I passed these videos on to them.

This is the first one. I got impatient at first and tried to skip because I thought the first two or three were below my skill level, but it is worth it to sit through all of them; it's a couple hours out of your day but I can subnet in my head for the most part now.

http://www.youtube.com/watch?v=UXN5XrmsaV8&feature=related

When you start to gain an understanding, this site is awesome:

http://subnettingquestions.com/

We all do twenty of these a week just as a refresher.
 
Last edited:
Can we sticky this already?
Subnetting the easy way!

CIDR:
When you've chosen a possible subnet mask for your network and need to determine the number of subnets, valid hosts, and broadcast addresses of a subnet that the mask provides, all you need to do is answer five simple questions:

How many subnets does the chosen subnet mask produce?
How many valid hosts per subnet are available?
What are the valid subnets?
What's the broadcast address of each subnet?
What are the valid hosts in each subnet?

At this point, it's important that you both understand and have memorized your powers of 2.

How many subnets? 2x = number of subnets. x is the number of masked bits, or the 1s. For example, in 11000000, the number of 1s gives us 22. In this example, there are 4 subnets

How many hosts per subnet? 2y- 2 = number of hosts per subnet. y is the number of unmakes bits, or the 0s. For example, in 1100000, the number of 0s gives us 26- 2 hosts. In this example, there are 62 hosts per subnet. you need to subtract 2 fro the subnet address and the broadcast address, which are not valid hosts.

What are the valid subnets? 256 - subnet mask = block size, or increment number. An example would be 256 - 192 = 64. The block size of a 192 mask is always 64. Start counting at zero in blocks of 64 until you reached the subnet mask value and these are your subnets. 0, 64, 128, 192. easy huh?

What's the broadcast address for each subnet? Now here's the really easy part. Since we counted our subnets in the last section as 0, 62, 128, and 192, the broadcast address is always the number right before the next subnet. For example, the 0 subnet has a broadcast address of 63 because the next subnet is 64. The 64 subnet has a broadcast address of 127 because the next subnet is 128. And so on. And remember, the broadcast address of the last subnet is always 255.

What are the valid hosts? Valid hosts are the numbers between the subnets, omitting the all 0s and all 1s. For example, if 64 is the subnet number and 127 is the broadcast address, then 65-126 is the valid host range-it's always the numbers between the subnet address and the broadcast address.

Practice Example for a Class B /23:
172.16.0.0 = Network Address
255.255.255.254.0 or /23 = Subnet

Subnets? 2^7 = 128
Hosts? 2^9 - 2 = 510
Valid Subnets? 256-254-0,2,4,6,8, etc up to 254
Braodcast address for each subnet?
Valid hosts?

Subnet 0.0 2.0 4.0 6.0 8.0
First Host 0.1 2.1 4.1 6.1 8.1
Last Host 1.254 3.254 5.254 7.254 9.254
Broadcast 1.255 3.255 5.255 7.255 9.255
 
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