Subnet Mask Learning

Sub netting Class Less Inter Domain Routing (CIDR) Class C IP 00000000=0 10000000=128 11000000=192 11100000=224/27 11110000=240/28 11111000=248/29 11111100=250 /30

/24 /25 /26

11111110=254 11111111=255 /32

/31

We don’t use that because at least 2 host bit is used for Assigning IP.

Example-1 192.168.10.0= Network Address 255.255.255.128= Subnet Mask Subnet= 21=2 Host = 27-2=126 Valid Subnets are: 256-128=128 0 and 128 Subnet First Host Last Host Broadcast

0 1 126 127

128 129 254 255

Example-2 255.255.255.192(/26) =11111111.11111111.11111111.11000000 192.168.10.0= Network Address 255.255.255.192= Subnet Mask Subnet= 22 =4 Host Per Subnet =26-2=62 Valid Subnets are: 256-192=64 0,64,128,192

Subnet First Host Last Host Broadcast

0 1 62 63

64 65 126 127

128 129 190 191

192 193 254 255

Example-3 Node Address: 192.168.10.174 Subnet Mask: 255.255.255.240 The mask is 240 Block Size is : 256-240=16 So the Blocks are: 0,16,32,48,64,80,96,112,128,144,160,176 So our host address 192.168.10.174 is between the block 160 and 176. Thus the subnet is: 160. The Broadcast address is: 175 So, finally the host range is : 161-174 Example-4 /26 = 11111111.11111111.11111111.11000000 -192 Subnet Mask -2 bit ON and 6 bit OFF (11000000=192) -Block Size: 256-192=64 -4 Subnet : 0,64,128,192 -No of Host in each subnet: 62 Class B IP 255.255.0.0 255.255.128.0 255.255.192.0 255.255.224.0 255.255.240.0 255.255.248.0 255.255.252.0 255.255.254.0

(/16) (/17) (/18) (/19) (/20) (/21) (/22) (/23)

Example-1 255.255.128.0 (/17)

=11111111.11111111.10000000.00000000

172.16.0.0= Network Address 255.255.128.0= Subnet Mask Subnet = 21=2 Host = 215-2=32,766 Valid Subnets are: 256-128=128 0, 128 Broadcast Addresses are: 127.255, 255.255 Subnet First Host Last Host Broadcast

0.0 0.1 127.254 127.255

128.0 128.1 255.254 255.255

Example-2 What subnet and broadcast address for IP address 172.16.10.33 and 255.255.255.224 (/27) Blocks Size: 256-224=32 Subnets are :0,32,64,….. IP address 172.16.10.33 is between the 32 and 64 So, Subnet: 10.32 Broadcast: 10.63 Class A IP 255.0.0.0 255.128.0.0 255.192.0.0 255.224.0.0 255.240.0.0 255.248.0.0 255.252.0.0 255.254.0.0

(/8) (/9) (/10) (/11) (/12) (/13) (/14) (/15)

255.255.0.0 Example -1

(/16)

255.255.240.0 (/16)=11111111.11111111.00000000.00000000 Subnet: 212=4096 Hosts: 212-2=4094 Block Size: 256-240=16 Subnets are: 0,16,32 etc. Subnet First host Last host Broadcast

10.0.0.0 10.0.0.1 10.0.15.254 10.0.15.255

10.0.16.0 10.0.16.1 10.0.31.254 10.0.31.255

.. .. .. ..

10.255.240.0 10.255.240.1 10.255.255.254 10.255.255.255