Tuesday, August 12, 2008

IP Addressing 2


Network ID Guidelines
The network ID identifies the TCP/IP hosts that are located on the same physical network. All hosts on the same physical network must be assigned the same network ID to communicate with each other.
Follow these guidelines when assigning a network ID:
The network ID must be unique to the IP internetwork. If you plan on having a direct routed connection to the public Internet, the network ID must be unique to the Internet. If you do not plan on connecting to the public Internet, the local network ID must be unique to your private internetwork.
The network ID cannot begin with the number 127. The number 127 in a class A address is reserved for internal loopback functions.
All bits within the network ID cannot be set to 1. All 1's in the network ID are reserved for use as an IP broadcast address.
All bits within the network ID cannot be set to 0. All 0's in the network ID are used to denote a specific host on the local network and are not routed.

lists the valid ranges of network IDs based on the IP address classes. To denote IP network IDs, the host bits are all set to 0. Note that even though expressed in dotted decimal notation, the network ID is not an IP address.
Class Ranges of Network IDs
Address Class
First Network ID
Last Network ID
Class A
1.0.0.0
126.0.0.0
Class B
128.0.0.0
191.255.0.0
Class C
192.0.0.0
223.255.255.0
Host ID Guidelines
The host ID identifies a TCP/IP host within a network. The combination of IP network ID and IP host ID is an IP address.
Follow these guidelines when assigning a host ID:
The host ID must be unique to the network ID.
All bits within the host ID cannot be set to 1 because this host ID is reserved as a broadcast address to send a packet to all hosts on a network.
All bits in the host ID cannot be set to 0 because this host ID is reserved to denote the IP network ID.
lists the valid ranges of host IDs based on the IP address classes.


Class Ranges of Host IDs
Address Class
First Host ID
Last Host ID
Class A
w.0.0.1
w.255.255.254
Class B
w.x.0.1
w.x.255.254
Class C
w.x.y.1
w.x.y.254

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