Subnetting example explained |
| Written by Mihai Dobos | |
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In this tutorial, I will show how to calculate subnets, network addresses and the number of hosts within a given IP and subnet mask.
We have the IP address of 192.32.65.10 with a CIDR (Classless Interdomain Routing standard) notation of /27. We have 3 IP classes to keep in mind:
A: 1.0.0.0 -> 127.255.255.255 with a mask of /8 by default These are specified by international organizations. We conclude that our IP address 192.32.65.10 is in class C. So by default, we have 24 bits for network part. But we applied 27 bits for this part, so 27-24 = 3 bits used for subnet. Keep this in mind.
Q: How do we calculate the number of subnets?
Q: How do we calculate the network address?
192.32.65.10=
1 AND 1 = 1
written by Ced , February 28, 2008
1. If you worked on an older network that could not interpret classless addressing, and your network ID was 145.27.0.0, what is the theoretical maximum number of different subnets you could create on this network? 2. You have decided to create 254 subnets on your Class B network. What subnet mask will you use to accomplish this? 3. If you subdivide your Class B network into 254 subnets, what is the maximum number of hosts you can assign to any single subnet? 4. Your company has leased a Class C network whose network ID is 205.61.128.0. You want to create 16 subnets within this network. One of the subnets will have an extended network prefix of 205.61.128.64. What will be the broadcast address for this subnet? (Hint: If you know the number of hosts per subnet, you can easily determine the broadcast address.) 5. What is Supernetting 6. How do you calculate a default gateway
written by Mihai Dobos , February 28, 2008
Hello Ced We are more then happy to answer your questions, but this does not include your homework assessments. To fully understand subnetting, read our tutorials related to this topic and do some exercises.
written by Boley, Emmanuel , March 16, 2008
can you send me a more detail lesson on this subject to my email box to help me out. Thanks. Boley
written by Boley, Emmanuel , March 16, 2008
The stuff is good and i like it...it comes down to your level. Even my kid knows what's in it to learn. Thanks
written by kondal , June 11, 2008
The given information is good.
written by Misty , September 25, 2008
I've looked at about five tutorials on this subject and I have to say that you explained it better than the rest. Thank you for writing this.
written by Emma , October 11, 2008
How can I create or develop a subnet scheme using IP addresses 10.1.1.1/24 and 192.168.11.0/24 respectively that will allow a network to support two subnets of up to forty (40)clients each? How many subnets must there be to allow future growth? Your efficient service is greatly appreciated in advance and I know your simple but profound explanation will help me understand how to calculate the subnets, host bits, and host IDs.
written by set , October 22, 2008
wats the answers to the questions above?
written by duddi , December 25, 2008
I have a network 172.16.0.0 and I need to subnet it into two subnets with 125 hosts, two subnets with 90 hosts, one subnet with 30 hosts, and 4 subnets with 2 hosts. Please help me
written by chuck paver , December 27, 2008
172.16.0.0 you need 9 subnets 2 hosts = /30 30 hosts = /27 90 hosts = /25 125 hosts = /25 start with the largest subnet you need: /25: A) 172.16.0.0/25 (3rd octet = 00000000); this satisfies 1 subnet offering 2^7 - 2 = 126 hosts B) next subnet = 172.16.0.128/25 (3rd octet = 00000000) 4th=(10000000) this satisfies 1 subnet offering 2^7 -2 = 126 hosts C) now at this point, we have answered the 125 host requirement. Let us move forward regarding the 90 host requirement. 2 subnets are needed, same mask--since no other mask would work. 172.16.1.0/25 (3rd octet = 00000001) (4th octet = 00000000) 172.16.1.128/25 (3rd octet = 00000001) (4th octet = 10000000) both solve the requirement for 90 hosts D) Next, look at /27 mask. we need only 1 subnet. We need to make sure that we do not overlap the previous subnets that we used. (you cannot take from the parent). therefore, we will use 172.16.4.0/27--i have chosen this arbitrarily, i could have chosen another combination. this gives us that 1 subnet. E) the final requirement calls for 4 subnets, each having a mask of /30 well, again, i can pick a different subnet: 172.16.5.0/30, .6.0/30, .7/0/30, and .8.0/30. here is how i did it, in case you are confused. 172.16.0.0/16 is the starting point. when you use vlsm, you can break it down by 1 bit at a time, but this takes a long time in your case: 172.16.0.0/17 and 172.16.128.0/17 then take 1 more bit we get 172.16.0.0/18 & 172.16.64.0/18 & 128.0/18 & 192.0/18 take one more bit we get 2^3 = 8 combinations): 172.16.0.0/19 & 32.0/19 & 64.0/19 & 96.0/19 ........etc... this takes forever, in your case. thus we can jump. we know the starting point is /25 since you have been asked to create 2 subnets containing 125 hosts each. 2^7-2 = 126. Thus, i will borrow 9 bits for the subnetting, leaving 7 bits for the host portion. borrowing 9 bits for hte host portion gives us 512 subnets. There is no way on earth we can realistically write all down in a given amt of time--its not practical. Thus you can pick the subnets. 172.16.00000000.0 0000000
written by sonu chaudhary , February 24, 2009
hi this sonu chaudhary from aligarh i have a qustion - Q.1 I have a network id 192.168.0.0/24. and i want 10 subnet and each should have 300 Host. please tell me.... Regards sonu chaudhary
written by president , April 21, 2009
I want to know with support of exemple how to customise subtenet
written by kimper , April 27, 2009
how do i calculate the subnet number? (not the number of subnets but rather the subnet number of the subnet that host is attached to) Do you need more help? Ask now!
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| Last Updated ( Thursday, 28 February 2008 ) |
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