Static IP Address
Static IP address is an address that is fixed and permanently assigned to a machine, unless manually changed. A Static IP address remains the same every time a user logs on or a machine boots up on the network. This type of address is provided by ISPs an additional cost.
Static IP addresses are configured by a network administrator individually on each machine. The advantage of this type of allocation is that the administrator has complete knowledge about the IP assigned to each machine.
The drawback is obviously the manual work and time involved. Imagine the time and workload involved in configuring thousands of computers in an organization.
Dynamic IP Address
A Dynamic IP address is an IP that is not fixed. ISPs deploy dynamic allocation of IPs to their clients. Dynamic IP addresses have proved to be a boon for network administrators, reducing manual work by tons.
Working
The whole concept of Dynamic IP addresses relies on something called a DHCP client-server model. The DHCP server is the boss and has all the information preconfigured. The Client (local machine) is configured to contact the DHCP server whenever it needs an IP. The DHCP server provides the client with all the necessary information needed for communication with the internet. There can be variations in ways a dynamic IP is assigned to a client.
- The DHCP server is configured to assign only one specific IP every time a particular machine requests for an IP. The Machines Mac-address is statically mapped to this IP. Although dynamic in terms of assignment this type of allocation is also called Static DHCP, because the machine always gets the same IP. A machine configured this way will always show the same IP each time it boots-up on the network.
- The DHCP server may be pre-configured to randomly assign any IP from a Block of IPs (collection of IPs) to any machine that requests it. When the machine logs-off or shuts-down, its IP is released back to the server. On re-login a different IP, any one available from the IP block is allocated.
Other Types
- Unicast IP Address : It is used to transmit information to a specific network device on the network.
- Broadcast IP Address : It allows information to be sent to all the computers on a given subnet rather than a particular machine. The exact notation can differ by the operating system, but the standard is laid out in RFC 919. The IP packets directed to the broadcast address are received by each and every machine on the subnet. It is generally used for mass communication such as a radio transmission over to multiple listeners.
The broadcast address is calculated by taking the bit complement of the subnet mask and then applying OR operation bitwise with the IP address.Example: To broadcast a packet to an entire class B subnet using a private IP address space, the broadcast address would be 172.16.255.255. This can be done with the help of the subnet mask; 255.255.0.0, and the IP address; for e.g. 172.16.48.196. The complement of the subnet mask is 0.0.255.255, and 172.16.48.196 || 0.0.255.255 = 172.16.255.255.
255.255.255.255 is a limited broadcast IP address, which does not reach every node on the Internet, only nodes on LAN.
- Multicast IP Address : Multicast IP addresses are reserved and used only for specific groups of machines residing in a large domain. For example, an IP packet destined for a multicast address will be sent only to machine which are part of that Multicast Group. The address range of class D IP addresses from 224.0.0.0 to 239.255.255.255, or equivalent 224.0.0.0/4, is particularly reserved for Multicasting.
Examples are RIP which uses 224.0.0.9 and OSPF which uses 224.0.0.5 address. - Private IP Address : These are local addresses which cannot be routed over the Internet. Two organizations can use the same private IP address. These addresses are free for use by anyone.
- Public IP Address : It is a unique IP address assigned by IANA (Internet Assigned Network Authority). Duplication of the public IP addresses is impossible; hence these addresses need to be bought.