Networking with Linux : Understanding IP Addressing and need of IPv6

Let me start with a very basic question. What is IP address?
IP Address is a unique address which identifies a node on network uniquely. No two nodes can have same IP address on a single network. That said, now let me tell you that most commonly we use IPv4 to identify nodes on the networks. IPv4 is of the format xxx.xxx.xxx.xxx. IP Addressing scheme consist of a node address, a network address, a broadcast address and a netmask. Let us look about these topics in some details.

• Node Address : It is a 32 bit or 4 bytes address which identifies a node within a network uniquely. Addresses are classified into five types.
  
  
  
  1. Class A : This Address is of the form NNN.HHH.HHH.HHH where N type of bits represent network address and H type of bits represents node address. To put it in simple term we can say that all the addresses from 0.0.0.0 to 127.255.255.255 belongs to this class.
     This class has two special IP series. 10.HHH.HHH.HHH belongs to local networks only. They cannot be distributed as public IP Addresses. 127.HHH.HHH.HHH is used for localhost i.e. node uses this IP to refer to itself.
  2. Class B : This Address is of the form NNN.NNN.HHH.HHH. We can say that IP belonging to the range 128.0.0.0 to 191.255.255.255 comes under this category.
     This class also has two special IP series. 172.16.0.0 to 172.31.255.255 belongs to local networks. Also 169.254.HHH.HHH is the IP given if DHCP client is not able to get an IP from the DHCP server.
  3. Class C : The Address type is NNN.NNN.NNN.HHH. IP range is from 192.0.0.0 to 223.255.255.255 and 192.168.NNN.HHH is used for local networks.
  4. Class C and D are used for multicast and research purpose. These are normally unavailable for general purposes.
  
  
  
  IPv4 can provide only a finite number of IPs which is not enough to cater to the needs of increasing network nodes. Here IPv6 comes in picture. Unlike IPv4 it consits of 16 bytes (not 6). But since the hardware is costly to implement for IPv6, its use is still not wide spread.
  
   I will update this post with info about Network and Broadcast address and Netmask. Also I will give a brief introduction to CIDR or Classless Interdomain Routing.