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IPv4 Address Classes (now obsolete)

Class

First Bits

IP Address Range

Description

A

0

0.X.X.X - 127.X.X.X

00000000.X.X.X - 01111111.X.X.X

  • 8-bits for network-prefix
  • 24 bits for host-suffix

B

10

128.X.X.X - 191.X.X.X

10000000.X.X.X - 10111111.X.X.X

  • 16-bits for network-prefix
  • 16 bits for host-suffix

C

110

192.X.X.X - 233.X.X.X

11000000.X.X.X - 11011111.X.X.X

  • 24-bits for network-prefix
  • 8 bits for host-suffix

D

1110

224.X.X.X - 239.X.X.X

11100000.X.X.X - 11101111.X.X.X

  • for multicast purposes

E

1111

240.X.X.X - 255.X.X.X

11110000.X.X.X - 11111111.X.X.X

  • for experimental purposes
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Source/Loopback/Localhost Address

Address Type & Network-Host Separation

Address Range

Total Number of Addresses

Class A

127.X.X.X

01111111.X.X.X

16,777,216 IP addresses

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Reserved/Private IP Address

Address Type & Network-Host Separation

Address Range

Total Number of Addresses

Class A

10.X.X.X

00001010.X.X.X

16,777,216 IP addresses

Class B

172.16.X.X - 172.31.X.X

10101100.00010000.X.X - 10101100.00011111.X.X

1,048,576 IP addresses

Class C in terms of first 3 bits

Class B in terms of network and host separation

192.168.X.X

11000000.10101000.X.X

65,536 IP addresses

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Multicast/Group/Class-D Address Types

Group Address Types

Address Range

Description

Local Scope Addresses

224.0.0.X

11100000.0.0.X

  • addresses are used on a local link
  • Time-To-Live (TTL) of 1
  • 224.0.0.1 - all hosts
  • 224.0.0.2 - all multicast routers
  • 224.0.0.5 - all OSPF
  • 224.0.0.6 - all OSPF DR (Designated Router)

GLOP

233.X.X.0 - 233.X.X.255

11101001.X.X.0 - 11101001.X.X.255

Transient Addresses - Global Range

224.0.1.0 - 238.255.255.255

  • 224.2.X.X in the multicast backbone (Mbone)

Transient Addresses - Site-Local Scope

239.253.0.0/16

Transient Addresses - Organization Local Scope

239.192.0.0/14

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