ip addressing – dotted-decimal notation an ip address is 32 bits in size

• IP Addressing – Dotted-Decimal Notation– An IP address is 32 bits in size– Every IP address is grouped into four 8-bit

octets– Octets are separated by decimal points– Valid octet numbers range from 0 to 255 and

represent a binary number

• IP Addressing (cont.)– Each address consists of two parts: network id and host

id– The network portion of an address indicates whether

the device belongs to a Class A, B, C, D, or E network– Some octet numbers are reserved for special functions

• Dotted decimal notation– “Shorthand” convention used to represent IP addresses

and make them more easily readable by people

Network Mask• Network id – bits in IP address that match the 1’s in

the network mask• Host id – bits in IP address that match the 0’s in the

network mask• Broadcast address – Network id and all 1’s for host

id• Lowest IP address in network – Network id plus 1• Highest IP address in network – Broadcast address

minus 1• Number of addresses in network is 2n – 2 where n is

number of bits in host id

Network Mask

11111111.11111111.11111111.00000000

255.255.255.0

Network ID Host ID

IP = 131.123.165.200MASK = 255.255.0.0 Network ID Host IDbroadcast addresshighest address in subnetlowest address in subnet

number of addresses in subnet

IP = 131.123.165.200MASK = 255.255.0.0 Network ID 131.123Host IDbroadcast addresshighest address in subnetlowest address in subnet

number of addresses in subnet

IP = 131.123.165.200MASK = 255.255.0.0 Network ID 131.123Host ID 165.200broadcast address highest address in subnet lowest address in subnet

number of addresses in subnet

IP = 131.123.165.200MASK = 255.255.0.0 Network ID 131.123Host ID 165.200broadcast address 131.123.255.255highest address in subnet lowest address in subnet

number of addresses in subnet

IP = 131.123.165.200MASK = 255.255.0.0 Network ID 131.123Host ID 165.200broadcast address 131.123.255.255highest address in subnet 131.123.255.254lowest address in subnet

number of addresses in subnet

IP = 131.123.165.200MASK = 255.255.0.0 Network ID 131.123Host ID 165.200broadcast address 131.123.255.255highest address in subnet 131.123.255.254lowest address in subnet 131.123.0.1

number of addresses in subnet

IP = 131.123.165.200MASK = 255.255.0.0 Network ID 131.123Host ID 165.200broadcast address 131.123.255.255highest address in subnet 131.123.255.254lowest address in subnet 131.123.0.1

number of addresses in subnet 65,534

IP = 131.123.165.200MASK = 255.255.255.0 Network ID Host IDbroadcast addresshighest address in subnetlowest address in subnet

number of addresses in subnet

IP = 131.123.165.200MASK = 255.255.255.0 Network ID 131.123.165Host IDbroadcast addresshighest address in subnetlowest address in subnet

number of addresses in subnet

IP = 131.123.165.200MASK = 255.255.255.0 Network ID 131.123.165Host ID 200broadcast addresshighest address in subnetlowest address in subnet

number of addresses in subnet

IP = 131.123.165.200MASK = 255.255.255.0 Network ID 131.123.165Host ID 200broadcast address 131.123.165.255highest address in subnetlowest address in subnet

number of addresses in subnet

IP = 131.123.165.200MASK = 255.255.255.0 Network ID 131.123.165Host ID 200broadcast address 131.123.165.255highest address in subnet 131.123.165.254lowest address in subnet

number of addresses in subnet

IP = 131.123.165.200MASK = 255.255.255.0 Network ID 131.123.165Host ID 200broadcast address 131.123.165.255highest address in subnet 131.123.165.254lowest address in subnet 131.123.165.1

number of addresses in subnet

IP = 131.123.165.200MASK = 255.255.255.0 Network ID 131.123.165Host ID 200broadcast address 131.123.165.255highest address in subnet 131.123.165.254lowest address in subnet 131.123.165.1

number of addresses in subnet254

CIDR – Classless Inter-Domain Routing

• Notation - net-address/n where n=number of bits in network-id

• Alternative to “mask” notation• E.g. 131.123.8.0/24 same as 131.123.8.0

with netmask 255.255.255.0• 131.123/16 Kent State Univ. Network• 131.123.8./22 College of Business

IP = 131.123.165.200MASK = 255.255.254.0 Network ID Host IDbroadcast addresshighest address in subnetlowest address in subnet

number of addresses in subnet

IP = 131.123.165.200MASK = 255.255.254.0254 = 11111110165 = 10100101 Network ID 131.123.10100100.0 131.123.164.0

Host IDbroadcast addresshighest address in subnetlowest address in subnet

number of addresses in subnet

IP = 131.123.165.200MASK = 255.255.254.0254 = 11111110165 = 10100101 Network ID 131.123.10100100.0 131.123.164.0

Host ID 0.0.00000001.200 0.0.1.200

broadcast addresshighest address in subnetlowest address in subnet

number of addresses in subnet

IP = 131.123.165.200MASK = 255.255.254.0254 = 11111110165 = 10100101 broadcast address 131.123.10100101.255131.123.165.255

highest address in subnetlowest address in subnet

number of addresses in subnet

IP = 131.123.165.200MASK = 255.255.254.0254 = 11111110165 = 10100101 broadcast address 131.123.10100101.255131.123.165.255highest address in subnet131.123.165.254lowest address in subnet131.123.164.1

number of addresses in subnet

IP = 131.123.165.200MASK = 255.255.254.0254 = 11111110165 = 10100101 

number of addresses in subnet

29-2 = 512-2 = 510

IP = 131.123.165.200MASK = 255.255.255.128 Network ID Host IDbroadcast addresshighest address in subnetlowest address in subnet

number of addresses in subnet

IP = 131.123.165.200MASK = 255.255.255.128

128 = 10000000200 = 11001000 Network ID Host IDbroadcast addresshighest address in subnetlowest address in subnet

number of addresses in subnet

IP = 131.123.165.200MASK = 255.255.255.128

128 = 10000000200 = 11001000 Network ID 131.123.165.10000000 131.123.165.128Host IDbroadcast addresshighest address in subnetlowest address in subnet

number of addresses in subnet

IP = 131.123.165.200MASK = 255.255.255.128

128 = 10000000200 = 11001000 Network ID 131.123.165.10000000 131.123.165.128

CIDR notation 131.123.165.128/25

IP = 131.123.165.200MASK = 255.255.255.128

128 = 10000000200 = 11001000 Network ID 131.123.165.10000000 131.123.165.128Host ID 0.0.0.01001000 0.0.0.72broadcast addresshighest address in subnetlowest address in subnet

number of addresses in subnet

IP = 131.123.165.200MASK = 255.255.255.128

128 = 10000000200 = 11001000 Network ID 131.123.165.10000000 131.123.165.128Host ID 0.0.0.01001000 0.0.0.72broadcast address

131.123.165.11111111 131.123.165.255highest address in subnetlowest address in subnet

number of addresses in subnet

IP = 131.123.165.200MASK = 255.255.255.128Network ID 131.123.165.10000000 131.123.165.128Host ID 0.0.0.01001000 0.0.0.72broadcast address

131.123.165.11111111 131.123.165.255highest address in subnet

131.123.165.254lowest address in subnet

131.123.165.129

number of addresses in subnet

IP = 131.123.165.200MASK = 255.255.255.128

highest address in subnet 131.123.165.254

lowest address in subnet 131.123.165.129

number of addresses in subnet 27-2 = 128-2 = 126