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IP Addressing

Every host on an IP based network has a unique IP address. IP addresses are 32bit addresses broken down into four 8bit segments (Example: decimal or binary 11111111.11111111.11111111.11111111). IP addresses are broken into two parts, the network and the host segments. They are determined by the subnet mask. When hosts are communicating if the network portion of their IP addresses are the same they will communicate directly, because they are on the same network segment. If the network part of the IP addresses are different the communication must be directed through a router since the clients are on different network segments. IP addresses are broken down into five address classes. The first octet of the address determine which class the address falls in.

Class Network ID Number of networks Hosts per network Default subnet mask
Class A - first octet 1-126 First Segment 126 16,581,373
Class B - first octet 128-191 First two segments 16,384 65,024
Class C - first octet 192-223 first three segments 2,097,152 254
Class D- first octet 224-239 is reserved for multicasting
Class E - first octet 240-255 Experimental not in use

Private IP addresses are special ranges are not on use on the public internet. They are reserved for use on local internal LAN environments. By not using these publicly on the internet it allows multiple companies to use them in internal network envoriments. This allows companies to use fewer public IP addresses.


127.x.x.x is reserved for loopback. The IP address used for loopback is

Network Management Protocols <<  1 2 3 4 5 6 7 8 9  >> TCP/IP Utilities
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