--- id: 1777871422-VTLQ aliases: - Subnetting (Part 2) tags: [] --- # Subnetting (Part 2) ## Question 45 hosts -> SW1->+--+<-SW3<-45 hosts |R1| 45 hosts -> SW2->+--+<-SW4<-45 hosts Divide the 192.168.1.0/24 network into four subnets that can accommodate the number of hosts required. The first subnet (Subnet 1) is 192.168.1.0/26 What are the remaining subnet Hint: Find the broadcast address of Subnet 1. The next address is the network address of Subnet 2. Repeat the process for Subnets 3 and 4 ### Subnet 1 Subnet 1: 192.168.1.0/26 11000000.10101000.00000001.00**000000** 192 . 168 . 1 . 0 broadcast address: 11000000.10101000.00000001.00**111111** 192 . 168 . 1 . 63 192.168.1.0 to 192.168.1.63 ### Subnet 2 Subnet 2: 192.168.1.64/26 11000000.10101000.00000001.01**000000** 192 . 168 . 1 . 64 11000000.10101000.00000001.01**111111** 192 . 168 . 1 . 127 192.168.1.63 to 192.168.1.127 ### Subnet 3 Subnet 3: 192.168.1.128/26 11000000.10101000.00000001.10**000000** 192 . 168 . 1 . 128 11000000.10101000.00000001.10**111111** 192 . 168 . 1 . 191 192.168.1.128 to 192.168.1.191 ### Subnet 4 Subnet 4: 192.168.1.192/26 11000000.10101000.00000001.11**000000** 192 . 168 . 1 . 192 11000000.10101000.00000001.11**111111** 192 . 168 . 1 . 255 192.168.1.192 to 192.168.1.255 ### Trick By adding 64 the last bit of the network portion you can find the network address ## Subnetting 11000000.10101000.00000001.0**0000000** 192.168.255.0 11000000.10101000.11111111.1**0000000** 192.168.255.0 Borrowing 1 bit = can make 2 subnets ### Formulas 2^x = number of subnets (x=number of 'borrowed' bits) 2^n-2 = number of hosts (x=number of hosts bits) ## Identify the subnet What subnet does host 192.168.5.57/27 belong to? 11000000.10101000.00000101.00111001 192.168.5.57 The borrowed bits are 11000000.10101000.00000101.**001**11001 to find the network address we need to change the host bits by zero 11000000.10101000.00000101.**001**00000 192.168.5.32 What subnet does host 192.168.29.219/29 belong to? 11000000.10101000.00011101.**11011**011 192.168.29.219 to find the network address we need to change the host bits by zero 11000000.10101000.00011101.**11011**000 192.168.29.216 ## Subnets / hosts (class C) | Prefix Length | Number of subnets | Number of Hosts | | ------------- | ----------------- | --------------- | | /25 | 2 | 126 | | /26 | 4 | 62 | | /27 | 8 | 30 | | /28 | 16 | 14 | | /29 | 32 | 6 | | /30 | 64 | 2 | | /31 | 128 | 0 (2) | | /32 | 156 | 0 (1) | ## Subenetting Class B The process of subnetting Class A, Class B and Class C networks is : Exactly the same ! ### Example 1 You have been given the 172.16.0.0/16 network. You are asked to create 80 subnets for your company's various LANs, What prefix length should you use ? 172.16.0.0/16 10101100.00010000.00000000.00000000 172 . 16 . 0 . 0 We have to borrow 7 bits = 128 subnets 10101100.00010000.**0000000**0.00000000 172 . 16 . 0 . 0 ### Example 2 You have been given the 172.22.0.0/16 network. You are asked to create 500 subnets for your company's various LANs, What prefix length should you use ? 172.22.0.0/16 10101100.00010000.00000000.00000000 172 . 22 . 0 . 0 We have to borrow 9 bits = 512 subnets = /25 10101100.00010000.**00000000.0**0000000 172 . 22 . 0 . 0 ### Example 3 You have given the 172.18.0.0/16 network. Your company requires 250 subnets with the same number of hosts per subnet. What prefix length should you use 172.18.0.0 10101100.00010000.00000000.00000000 172 . 18 . 0 . 0 We have to borrow 8 bits = 256 subnets = /24 10101100.00010000.**00000000**.00000000 172 . 18 . 0 . 0 ## Subnets / hosts (class B) | Prefix Length | Number of subnets | Number of Hosts | | ------------- | ----------------- | --------------- | | /17 | 2 | 32766 | | /18 | 4 | 16382 | | /19 | 8 | 8190 | | /20 | 16 | 4094 | | /21 | 32 | 2044 | | /22 | 64 | 1022 | | /23 | 128 | 510 | | /24 | 256 | 254 | | /25 | 2 | 126 | | /26 | 4 | 62 | | /27 | 8 | 30 | | /28 | 16 | 14 | | /29 | 32 | 6 | | /30 | 64 | 2 | | /31 | 128 | 0 (2) | | /32 | 156 | 0 (1) | ## Review - Subnetting practice questions (class C networks) - Subnetting Class B networks