CIM 2465 IP Subnetting1 IP Subnetting Textbook: Networking Basics, CCNA 1 Companion Guide, Cisco Press Cisco Networking Academy Program, CCNA 1 and 2, Companion Guide, Cisco Press, Latest Edition

CIM 2465 IP Subnetting2 Brief Review Rules? Terms –Subnet –Subnet Number –Subnet Mask

CIM 2465 IP Subnetting3 Determining the Number of Required Subnets and the Resulting Subnet Mask To come up with a subnetting plan (subnetting scheme), the engineer must answer the following questions: –How many subnets are required for a particular network? –What is the largest number of hosts needed in the largest subnet? –How many subnet bits does the subnet mask need to support (at least) that many subnets? –How many host bits does the subnet mask need to support (at least) that many hosts per subnet? –What subnet mask(s) support(s) the required number of subnet and host bits?

CIM 2465 IP Subnetting4 Number of Subnets and Hosts

CIM 2465 IP Subnetting5 Number of Subnet and Host Bits

CIM 2465 IP Subnetting6 How to find? Number of required subnet bits (in mask) –Find the number s such that 2 S – 2 >= the number of required subnets Number of required host bits (in mask) –Find the number h such that 2 h – 2 >= the number of required hosts

CIM 2465 IP Subnetting7 Examples Required Number of Subnets Required Number of Hosts Min Subnet bits needed Min Host bits needed

CIM 2465 IP Subnetting8 Determine the Mask NetworkNumber of Subnet Bits Number of Host Bits Mask

CIM 2465 IP Subnetting9 Determine Subnet Numbers and Assignable IP Addresses in Each Subnet Subnet number –The numerically lowest number in a subnet, represents a particular IP subnet Subnet broadcast address –The highest numerical value in a subnet, for broadcast Assignable IP address –IP addresses that may be assigned to an interface Subnet zero (zero subnet) –The numerically smallest subnet number. With classful IP addressing, not be used Broadcast subnet –The numerically largest subnet number, With classful IP addressing, not be used

CIM 2465 IP Subnetting10

CIM 2465 IP Subnetting11 Case Class C network: Mask:

CIM 2465 IP Subnetting12 Finding Subnets * *

CIM 2465 IP Subnetting13 Finding Subnet Broadcast Address * *

CIM 2465 IP Subnetting14 Range of Valid Addresses SubnetLowest IPHighest IPBroadcast * *