Hope you like this subnetting tutorial. Subnetting is foundation, you have to build it as strong as you can!! You will be able to do subnetting on the fly, Practice is the key. You can verify your answers using Subnet Calculator while practicing. Subnetting Tutorial - Subnetting Explained with Examples This tutorial is the third part of the article. It explains the Subnetting concepts and terms such as network id, broadcast id, total hosts, valid hosts, power of 2, block size and CIDR in detail.

Welcome to the subnetting.net subnetting tutorial. This training session will teachyou everything you need to know to pass any exam that requires TCP/IP knowledge.In addition, the methods you will learn here will allow you to not only solve subnettingquestions, it will help you increase your speed and master TCP/IP concepts.For many entry-level to intermediate computer networking exams, the need to quicklysolve subnet based questions is apparent. In addition, the mastery of these conceptswill give you a major advantage when you sit for the exam. For example, some haveestimated that the CCNA exam has around 40% subnetting questions. When you are donewith this tutorial, these questions will be no harder than simple addition or subtraction.To put this is real life terms, suppose the CCNA exam has 50 questions and you are givenaround 20 subnetting questions.

When you learn to subnet, you should expect to acethese 20 questions. In other words, you would get 100% on 40% of the exam. This makesthe remainder of your study time much more productive. TCP/IP Subnetting Very BasicThe first thing we need to look at is - What is an IP address? How does it work?Here is kind of a loose analogy that should make this very clear. Think of an IPaddress as your postal address.

Let's take 191.54.38.15 for example. In our analogy,each set of numbers may represent a geographic area. As we move from the left tothe right, the geographic area continuously becomes more and more specific.191 = Your State54 = Your Town38 = Your Apartment building15 = Your Apartment NumberTo have TCP/IP, at some point, you must have a router. It doesn't make much differenceif you have a router in your house, or a router in your business. They basicallyprovide the same functionality. To further this analogy, think of a router as apost office.

TCP/IP Address ConstructA TCP/IP address is a 32 bit, binary number that has been converted to decimal.Whenever the word binary comes up, many people immediately become concerned. Noworries, this is going to be very easy. Here are a few simple definitions to helpthe process:Octet = An octet is simply a group of 8 numbers. The IP address 191.168.1.1 hasfour octets: 191, 168, 1, and 1.

I know I said there are 8 numbers and I only showedyou four, but keep in mind that IP is in binary, not decimal. Each set of numbersrepresent 8 binary digits (zeroes or ones).Bits = A bit is simply a single character. In other words, 32 bits equals 32 zeroesor ones.Binary = A number system that is based on two characters - 0 & 1.Okay, now let's convert our decimal IP address of 191.54.38.15 into binary:Remember that each octet represents eight binary digits - Each placement of thosebinary digits represents a decimal number. To start, let's look at a simple threedigit binary number:-421Our decimal numbers on the bottom always start with 1 and double for each placementgoing from right-to-left. To convert to a decimal number, we will add a 1 aboveevery decimal number we want to add together to get to our decimal number and azero for every number we are not going to add.Decimal Number 3011-421Now we simply add each decimal number (on the bottom) each time we see a binary1. Thus, decimal 3 = 011Decimal 4 = Binary 100100-421Decimal 5 = Binary 101101-421Decimal 191 = Binary 111111-421Decimal 54 = Binary 110110-421Decimal 38 = Binary 100110-421Decimal 15 = Binary 001111-1111191.54.38.15 = 101010.00001111.

Subnet MaskA subnet mask is used to determine where the network ends and the hosts begin. Weget this information by converting the decimal numbers within the subnet mask tobinary. The 1's in our binary subnet mask represents the network portion of ourIP address, and the 0's represent the hosts.

Here's an example:IP Address: 192.168.1.0Subnet Mask: 255.255.255.0The first thing we do is convert our first octet to binary:11111111-421When we add up all the decimal numbers underneath our binary 1's, we get 255 (128+64+32+16+8+4+2+1).In this example, the next two octets are also all 1's. And as you probably haveguessed the fourth and final octet in our example is all 0's or all hosts.So in binary, 255.255.255.0 is equal to:111111.00000000Wherever our 1's stop and our zeros begin is called our network boundary:111111. 00000000In this example, the first three octets are our network and the last one representsour hosts:Subnet = 192.168.1.0Hosts. = 192.168.1.1 - 192.168.1.254 (E.g.

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2, 192.168.1. 3,etc.).The number of hosts on any network is determined by taking 2 to the power of the number of binaryzero's.

In this example, 8 0's = 2^8 = 256. However, we haveto remove the first and last address from the pool of usable addresses.

We willdiscuss this later, for now suffice it to say that the actual formula to determinehow many hosts is (2^n)-2, where n = the number of binary zero's.In our example n=8, so we have 2^8-2=256-2=254. IP Address ClassesThere are five classes of IP addresses: ClassPurposeFirst Octet RangeMaximum HostsTotal NetworksClass AVery Large Networks1-126.16,777,216 (2^24)128 (2^7)Class BLarge Enterprise128-19165,536 (2^16)16,384 (2^14)Class CSmall Business192-223256 (2^8)2,097,152 (2^21)Class DMulticast224-239N/AN/AClass EExperimental240-255N/AN/A.IP addresses that begin with 0 or 127 are reserved for various functions.Some find it easier to remember these addresses via the first binary bits of eachnetwork type:0 = Class A10 = Class B110 = Class C1110 - Class D1111 - Class E. Private Network RangesEach class of IP addresses has a private address range.These ranges were created to conserve public IP addresses.Instead of issuing a real IP address to every host on your network, you can issue a private address and translate the private address to a public one when you communicate with the Internet.For example, a network with 200 or even 200,000 hosts, could use just one public IP address.This process is called NAT/PAT and will be covered in another lesson.Class A Private Address = 10.0.0.0/8. If an IP address begins with the number 10, it is a class A private address.Class B Private Address = 172.16.0.0/12. If an IP address begins with 172.16-31, it is a class B private address.Class C Private Address = 192.168.0.0/16. If an IP address begins with 192.168, it is a class C private address.Chances are if you look at the IP address of your PC right now, you will have a private IP address in one of the above ranges.If you are at home, your router is likely running DHCP and issued your PC a private IP Address.When you communicate on the Internet, the public IP address that has been issued by your ISP will be used.The router in your home is translating your private address to your public address.Key Topic: A private IP address cannot be routed over the Internet, but can be routed throughout your internal network. Subnet 0In the not too distant past, it was considered bad practice to use the first networkin your subnet range.

For example, if we had the IP range of 192.168.1.1 255.255.255.192,our networks would be:192.168.1.0, 192.168.1.64, 192.168.1.128, 192.168.1.192In this example, the first network (192.168.1.0) would not be used. However, thiscommand in Cisco equipment is really never used and the default Cisco settings assumesubnet 0 will always be used. If you take a Cisco exam and they indicate that thesubnet zero command is on, you have to remove the first network from your calculations.However, chances are this will not happen on any current exam. You should alwaysassume the first network can be used unless you are told otherwise.

Question Type 1 Video Example:Question Type 1 Written Example: What is the Network ID, Broadcast Address, First UsableIP, or Last Usable IP on the subnetwork that the node 192.168.1.15/26 belongs to?No matter which of the four criteria the question asks, you should always followthese identical steps. This makes solving the actual question very easy.Step 1. Convert the shorthand subnet mask to decimal.

/26 = 255.255.255. + Two additional subnet bits.

Go to your cheat sheet, start at the bottom (128) and count up two, starting with128. You should get to 192. Thus, our decimal subnet mask is 255.255.255.192Step 2.

Determine the block size. The block size is listed in the block size column parallel to your decimal mask. The block size is 64.Step 3. What is my Network ID?. Since we are working in the fourth octet and the block size is 64, the first networkis 192.168.1.0.Step 4.

What is the next Network ID?. Again, we look at our block size of 64 to determine the next network is 192.168.1.64. Network ID (First IP in the subnet): 192.168.1.0.

Broadcast address (last IP in the subnet): 192.168.1.63. First Usable IP (the address after the network ID): 192.168.1.1. Last Usable IP (the address before the broadcast address): 192.168.1.62Notes: The block size determines the networks. Since the block size is 64, our networksare 192.168.1.0, 192.168.1.64, 192.168.1.128, and 192.168.1.192. To determine yournetwork, you just have to find the range that includes your IP address. In thisexample, it is the first network. If your IP was 192.168.1.72, you would belongto the second network 192.168.1.64 - 192.168.1.127.Let's quickly go through one more: Enter the last valid host on the network that the host 172.30.118.230/23 is a part of:Step 1.

Convert the shorthand subnet mask to decimal. /23 = 255.255. + Seven additional subnet bits. Go to your cheat sheet, start at the bottom (128) and count up seven, starting with 128.

You should get to 254. Thus, our decimal subnet mask is 255.255.254.0.Step 2. Determine the block size. The block size is listed in the block size column parallel to your decimal mask. The block size is 2.Step 3. What is my Network ID?.

Since we are working in the third octet and the block size is 2, the first network is 172.30.118.0. (2. 59 = 118).We are simply looking for the largest multiple of the block size without going over the given octet number (118).Step 4. What is the next Network ID?. Again, we look at our block size of 2 to determine the next network is 172.30.120.0 (118 + 2).

Network ID (First IP in the subnet): 172.30.118.0. Broadcast address (last IP in the subnet): 172.30.119.255. First Usable IP (the address after the network ID): 172.30.118.1.

Last Usable IP (the address before the broadcast address): 172.30.119.254 (This is the answer to the specific question that was asked.). Question Type 3 Video Example:Question Type 3 Written Example: You have been asked to create a subnet mask for the 172.16.0.0network. Your organization requires 900 subnets, with at least 50 hosts per subnet.What subnet mask should you use?Step 1: Determine how many subnet bits (1's), you have to add to the classful boundaryto cover the number of required subnets. The IP address given was a class B address, making the first 16 subnet bits static. Using the cheat sheet, find the exponent of 2 that is equal to or greater than thenumber of subnets we require (900).

We can quickly see that 10 additional subnetbits will give us 1,024 subnets. Make note of the corresponding subnet mask. Inthis case, 255.255.255.192. The third octet is eight 1's, and the four is two 1's.We can count up from the bottom on our cheat sheet to get to 192.Step 2: Confirm the number of remaining 0's will cover our required hosts. In thiscase, there are 6 remaining 0's - 2^6-2=62, which is more than enough for our hostrequirements.Our subnet mask is 255.255.255.192. Giving us 1024 subnets and 62 hosts per subnet.For more examples, visit our page.

Variable Length Subnet Mask (VLSM)You are a network administrator and you have been assigned the task of setting upthe IP network. You have a single class C IP address range and have to setup thefollowing networks:. Network A = 100 Hosts.

Network B = 40 Hosts. Network C = 20 hosts. Network D = 10 hosts.

Network E = 6 Hosts. Network F = 2 HostsIP RangeNetworkNum IPsSubnet Mask0-127Network A128/25128-191Network B64/26192-223Network C32/27224-239Network D16/28240-247Network E8/29248-251Network F4/30It's really that easy:. Add up all host requirements to make sure you have enough in a single block. Work from the top down (largest host requirements) removing the number of required hosts for each network. Route SummarizationA summarized route can increase performance of a router by limiting the route table and reducing routing traffic.

IntroductionUnderstanding IP subnetting is a fundamental requirement for almost any techie - whether you’re a coder, a database administrator or the CTO. However, as simple as the concepts are, there is a general difficulty in understanding the topic.Here we’ll break this topic into eight simple steps and help you put the pieces together to fully understand IP subnetting.These steps will give you the basic information needed in order to configure routers or understand how IP addresses are broken down and how subnetting works. You'll also learn how to plan a basic home or small office network.A basic understanding of how binary and decimal numbers work is required. In addition, these definitions and terms will get you started:.: A logical numeric address that is assigned to every single computer, printer, switch, router or any other device that is part of a TCP/IP-based network.: A separate and identifiable portion of an organization's network, typically arranged on one floor, building or geographical location.: A 32-bit number used to differentiate the network component of an IP address by dividing the IP address into a network address and host address. (NIC): A computer hardware component that allows a computer to connect to a network.