Week 9 - IPv4 Subnetting and VLSM (1).pptx

Week 9: IPv4 Subnetting and VLSM NTWK8021 – Network Planning What we covered last lecture • Numbering Systems • IPv4 and IPv6 addressing Q/A Any Questions? Welcome to Week 9! This week, we are going to discuss IPv4 Subnetting and VLSM After this lecture, you should be able to… • • • • Learn...

Week 9: IPv4 Subnetting and VLSM NTWK8021 – Network Planning What we covered last lecture • Numbering Systems • IPv4 and IPv6 addressing Q/A Any Questions? Welcome to Week 9! This week, we are going to discuss IPv4 Subnetting and VLSM After this lecture, you should be able to… • • • • Learn about the importance of subnetting Understand CIDR Notation Understand the difference between normal subnetting and VLSM Go through subnetting examples Part 1: IPv4 Subnetting and VLSM NTWK8021 – Network Planning Types of Subnetting • Subnetting • VLSM Subnetting Definition of Subnetting • A networking technique used to divide larger network blocks into smaller segments • Has been around longer then VLSM Benefits of Subnetting • • • • Reduced network traffic Optimized network performance Simplified Management Better Problem Isolation Knowledge Required to Subnet • Binary Number Conversions • IP addressing – Knowing the network portion and host portion of an IP address and how to calculate it • Subnet Masks Subnet Masks • The subnet mask in IP addressing is used to identify the network portion and host portion of an IP address • One of the most common subnet masks in networking is 255.255.255.0 • The first three octets are ON, indicating that they belong to the network portion • The remaining bits are OFF giving us the host portion Subnet Mask in Binary • 255.255.255.0 converted to binary is… 111111111.111111111.11111111.00000000 • If we count how many bits are ON, it equals 24 • If we count how many bits are OFF, it equals 8 Subnetting vs VLSM • Normal subnetting works in cases where each subnet has the same number of devices • Relies on the Classful System, Class A, Class B and Class C • Considered legacy and no longer used today • VLSM is used when you want subnets of different sizes by utilizing CIDR • VLSM is considered classless and is the standard used today What is VLSM? • Stands for Variable Length Subnet Masking • A more advanced form of subnetting that’s used in scenarios where subnets have a varying number of clients or hosts • Utilizes the CIDR Notation What is CIDR? • Stands for Classless Inter-Domain Routing • Identifies the number of bits that belong to the network portion • In a previous slide, we identified the CIDR notation for 255.255.255.0, which is /24 • Example IP – 192.168.1.2/24 Common CIDR Notations • /32 – Commonly used to identify a single host • /30 – Used for point-point connections between devices (Commonly Routers) • /24 – Most common for LAN (Class C) allows for 254 usable address Components of CIDR CIDR Blocks and Subnet Masks CIDR Values Determining the Boundaries of Each Subnet • Find Your Network IDs – Identify the block size – Increment in the subnet portion in block size intervals, starting with the “classful” Net ID • Find Your Broadcast Addresses – This is the last IP address before the next Net ID in each block • Identify the IP addresses in the subnet – Each subnet starts with the first address after the Net ID and ends at the last address before the broadcast address Class C Subnets Part 2: VLSM Examples NTWK8021 – Network Planning Subnetting Class C 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? Practice Example #1C: 255.255.255.128 (/25) • Because 128 is 10000000 in binary, there is only 1 bit for subnetting, and there are 7 bits for hosts. We’re going to subnet the Class C network address 192.168.10.0. • 192.168.10.0 = Network address • 255.255.255.128 = Subnet mask • Now, let’s answer the big five: • How many subnets? Because 128 is 1 bit on (10000000), the answer is 21 = 2. • How many hosts per subnet? We have 7 host bits off (10000000), so the equation is 27 – 2 = 126 hosts. • (continued….) /25 continued • What are the valid subnets? 256 – 128 = 128. Remember, we’ll start at zero and count in our block size, so our subnets are 0, 128. • What’s the broadcast address for each subnet? The number right before the value of the next subnet is all host bits turned on and equals the broadcast address. For the 0 subnet, the next subnet is 128, so the broadcast of the 0 subnet is 127. • What are the valid hosts? These are the numbers between the subnet and broadcast address. The easiest way to find the hosts is to write out the subnet address and the broadcast address. This way, the valid hosts are obvious. /25 continued Subnet Example /25 Practice Example #2C: 255.255.255.192 (/26) • In this second example, we’re going to subnet the network address 192.168.10.0 using the subnet mask 255.255.255.192. – 192.168.10.0 = Network address – 255.255.255.192 = Subnet mask • It’s time to answer the big five: • How many subnets? Because 192 is 2 bits on (11000000), the answer is 22 = 4 subnets. • How many hosts per subnet? We have 6 host bits off (11000000), so the equation is 26 – 2 = 62 hosts. • What are the valid subnets? 256 – 192 = 64. Remember, we start at zero and count in our block size, so our subnets are 0, 64, 128, and 192. Practice Example #2C: 255.255.255.192 (/26) • What’s the broadcast address for each subnet? The number right before the value of the next subnet is all host bits turned on and equals the broadcast address. For the 0 subnet, the next subnet is 64, so the broadcast address for the 0 subnet is 63. • What are the valid hosts? These are the numbers between the subnet and broadcast address. The easiest way to find the hosts is to write out the subnet address and the broadcast address. • This way, the valid hosts are obvious. The following table shows the 0, 64, 128, and 192 subnets, the valid host ranges of each, and the broadcast address of each subnet: Practice Example #2C: 255.255.255.192 (/26) Okay, again, before getting into the next example, you can see that we can now subnet a /26. And what are you going to do with this fascinating information? Implement it! We’ll use the figure on the next slide to practice a /26 network implementation. Implementing a Class C /26 VLSM Example with a /16 VLSM Example with a /16 Answer Slides • The next set of slides goes through a method of subnetting the network in the diagram to meet the solution VLSM Chart for number of computers per CIDR Mask CIDR Notation Total IPs /24 256 /16 65536 /25 /26 128 /27 64 /17 /18 /19 32768 16384 /28 32 /29 16 /20 8192 /30 8 /21 4096 /31 4 /22 2048 /32 2 /23 1024 512 1 Answer Part 1 Subnet for 1912 Computers is /21 (2048) Network Address /21 subnet mask in decimal /21 subnet mask in binary First Address Last usable Address Broadcast Next Network Start 172.16.0.0 /21 255 11111111 172 172 172 172 255 248 0 11111111 11111000 00000000 16 0 1 16 7 254 16 7 255 16 8 0 Answer Part 2 Subnet for 435 computers is / 23 (512) Network Address /23 subnet mask in decimal /23 subnet mask in binary First Address Last usable address Broadcast Next Network Start 172.16.8.0 /23 255 11111111 172 172 172 172 255 254 0 11111111 11111110 00000000 16 8 1 16 9 254 16 9 255 16 10 0 Answer Part 3 Subnet for 238 Computers is /24 (256) Network Address /24 subnet in decimal /24 subnet in binary First Address Last usuable address Broadcast Address Next Network Start 172.16.10.0 / 24 255 11111111 172 172 172 172 255 255 0 11111111 11111111 00000000 16 10 1 16 10 254 16 10 255 16 11 0 Answer Part 4 Subnet for 2 devices is /30 (4) /30 subnet in decimal /30 subnet in binary First address Last usable address Broadcast Address Next Network Start 172.16.11.0/30 255 11111111 172 172 172 172 255 255 11111111 11111111 16 11 16 11 16 11 16 11 252 11111100 1 2 3 4 Q/A Any Questions? Part 3: Practical Assignment NTWK8021 – Network Planning Practical Assignment • Practical Assignment 1 is assigned today • We will now go through the Practical Assignment 1 document • See the instructional plan and assignment folder for the exact due date/time in Week 13 Q/A – End of Lecture Any Questions?