ip address doubt..

[gaurav@digit]

hi guys..
could anyone plz explain to me what actually the term network id means in the discussion of ip address classes..when i was goin through the online resources,i noticed that they all have discussed bout it but none have a clear description of the term..
What does it mean by class A has 126 networks and so on ..plz.. help

[Pragadheesh]

A network ID refers to a part of a TCP/IP address that is used to identify the subnet that a host may be on. The subnet that the computer is on is determined by the netmask and IP address of the computer. This subnet address is the same as the network ID and is the beginning part of the computers IP address.
When the netmask is setup, it is a number where some of the most significant bits have a 1's value and the rest have values of 0. The most significant part of the netmask with bits set to 1's specifies the network address, and the lower part of the address will specify the host address.
The part of the IP address that matches the part of the netmask where the bits are set to ones determines the network ID.

What does it mean by class A has 126 networks

have a glance at Classfull addressing and stuffs. ClassA has net id of 8bits so 2^8 i.e 128 networks are possible of which few are reserved.

here are links briefing about IP addressing.
IP Addressing
http://en.wikipedia.org/wiki/Classful_network

[gaurav@digit]

thank u Pragadheesh..it was helpful..