A class C address of /24 has been allocated. Perth, Sydney, and Singapore have a WAN connection to Kuala Lumpur. • Perth requires 60 hosts. • Kuala Lumpur requires 28 hosts. • Sydney and Singapore each require 12 hosts. To calculate VLSM subnets and the respective hosts allocate the largest requirements first from the address range. Requirements levels should be listed from the largest to the smallest. In this example Perth requires 60 hosts. Use 6 bits since 26 – 2 = 62 usable host addresses. Thus 2 bits will be used from the 4th Octet to represent in the extended-network-prefix of /26 and the. | Cisco Svstems I Lab Calculating VLSM Subnets Objective Use variable-length subnet mask VLSM to support more efficient use of the assigned IP addresses and to reduce the amount of routing information at the top level. Background Preparation A class C address of 24 has been allocated. Perth Sydney and Singapore have a WAN connection to Kuala Lumpur. Perth requires 60 hosts. Kuala Lumpur requires 28 hosts. Sydney and Singapore each require 12 hosts. To calculate VLSM subnets and the respective hosts allocate the largest requirements first from the address range. Requirements levels should be listed from the largest to the smallest. In this example Perth requires 60 hosts. Use 6 bits since 26 - 2 62 usable host addresses. Thus 2 bits will be used from the 4th Octet to represent in the extended-network-prefix of 26 and the remaining 6 bits will be used for host addresses. Step 1 The first step in the subnetting process is to divide the allocated address of 24 into four equal size address blocks. Since 4 22 2 bits are required to identify each of the 4 subnets. Next take subnet 0 26 and identify each of its hosts. Allocated Address Sub-networks 62 usable hosts sub-network subnet 0 24 26 26 Network Address 26 26 26 26 26 26 thru 26 26 26 Broadcast Address Here is the range for the 26 mask. 1 - 4 CCNA 3 Switching Basics and Intermediate Routing v - Lab Copyright 2003 Cisco Systems Inc. Perth Range of addresses in the last octet 26 From 0 to 63. 60 hosts required. Host 0 and 63 cannot be used as they are the network and broadcast addresses for their subnet Step 2 Allocate the next level after all the requirements are met for the higher level or levels. Kuala Lumpur requires 28 hosts. The next available address after 26 is .
