IPv4 Addresses
Chapter 5
1
Classful Addressing
239
2
Address Space
3
Netid and Hostid
4
Two-Level Addressing
netid
000 ... 0
First address
5
Network Mask
6
Three-Level Addressing: Subnetting
7
Subnetting
Network mask:
Subnet mask:
11111111.11111111.00000000.00000000
11111111.11111111.11000000.00000000
8
Supernetting
9
Supernetting - Example
10
Classless Addressing (CIDR)
11
Example
Address:
167.199.170.82/27
First Address:
167.199.170.64/27
Last Address:
167.199.170.95/27
12
Subnetting
A block of 256 addresses (14.24.74.0/24) is divided into 3
subblocks of 120, 60, and 10 addresses.
14.24.74.11001111
14.24.74.207/28
14.24.74.01111111
14.24.74.127/25
14.24.74.00000000
14.24.74.10111111
14.24.74.191/26
14.24.74.10000000
14.24.74.192/28
14.24.74.11000000
13
Address Allocation
ISP granted a block: 190.100.0.0/16 (65,536 addresses)

Group 1 has 64 customers; each needs 256 addresses


Group 2 has 128 customers; each needs 128 addresses


Total addresses: 16,384 = 214
Total addresses: 16,384 = 214
Group 3 has 128 customers; each needs 64 addresses

Total addresses: 8,192 = 213
14
Address Allocation


64 customers
Each customer needs
256 addresses
190.100.0.0/18


128 customers
Each customer needs
128 addresses
190.100.64.0/18


190.100.128.0/19
128 customers
Each customer needs
64 addresses
15
Special Addresses








Addresses reserved for special purposes
All-Zeros Address
All-Ones Address (Limited Broadcast Address)
Direct Broadcast Address
Loopback Addresses
Private Addresses
Multicast Addresses
Network Address
16
All-Zeros Address
Source: 0.0.0.0
Destination: 255.255.255.255
Packet
17
All-Ones Address: Limited Broadcast Address
Network
221.45.71.64/24
221.45.71.126/24
Destination IP address:
255.255.255.255
Packet
221.45.71.20/24
221.45.71.178/24
Router blocks
the packet
18
Direct Broadcast Address
Network: 221.45.71.0/24
221.45.71.64/24
221.45.71.126/24
221.45.71.178/24
221.45.71.20/24
Packet
Prefix
Specific
Suffix
All 1s
Destination IP address:
221.45.71.255
19
Loopback Addresses
Process 1
Process 2
Application layer
Transport layer
Packet
Network layer
Destination address:127.x.y.z
20
Private Addresses
21