- What is an IP address?
IP address is an network layer protocol address for a host in a TCP/IP network.
- What is the use of an IP address?
IP address is used to uniquely identify each host in a network. IP address is
needed in order to communicate with other hosts in the network using the TCP/IP
suite of protocols.
- Which version of IP is covered by this document?
This document covers IP version 4.
- Which RFC specifies the IP address standard?
RFC 1166 specifies the IP Version 4 address format.
- How a host determines its IP address?
A host determines its IP address during the boot-up process either from a
configuration file stored in the local hard disk of the system or using a
network protocol like RARP, DHCP, BOOTP from the servers in the network.
- Is there any relation between the MAC address and IP address of a host?
No. There is no relation between the MAC address and the IP address of a host.
- Can a single network interface have more than one IP address associated with it?
Yes. It is possible to associate more than one IP address to a single network
interface. This is discussed in detail in RFC 1122.
- What is the difference between a host name and an IP address?
A host name is used to identify a host by human beings and higher level user
applications. But IP protocol uses only IP addresses to identify a host in the
network. A host-name is provided just as a convenience for users of the
network and higher level applications.
- How a host name is resolved to the corresponding IP address?
A host name is resolved to the corresponding IP address either from a
configuration file stored in the local machine or using a network protocol like
DNS or WINS from a server in the network.
- What is the size of an IP address?
The size of an IP address is 32 bits (4 bytes).
- How an IP address is represented?
The following notation is used to represent an IP address. This notation is
called the dotted decimal format: M.N.O.P, where M, N, O and P represent the
first, second, third and fourth bytes of an IP address respectively. The size
of each byte is 8 bits and the value of each byte can be from 0 to 255. For
example, 192.9.205.21 is an IP address.
- What are the components of an IP address?
A IP address consists of the following components: Network ID and Host ID. For
example, in the IP address 192.9.205.21, the network ID is 192.9.205 and the
host ID is 21.
- What is a network ID?
A network ID uniquely identifies a network. All the hosts in a single network
will have the same network ID. For example, in the IP address 192.9.205.21,
the network ID is 192.9.205. A router analyses only the network ID portion of
an IP address for datagram forwarding.
- What is a host ID?
A host ID uniquely identifies a host in a network. Two hosts in two different
networks can have the same host ID. For example, in the IP address
192.9.205.21, the host ID is 21.
- What is a unicast IP address?
A unicast IP address is an IP address uniquely identifying a host in a network.
The datagram with a unicast IP address is received and processed by only a
single host. For example, the IP address 192.9.205.21 is a unicast IP address.
- What is a multicast IP address?
A multicast address is an IP address identifying a particular group of hosts in
network. This group of hosts is called a multicast group. For example, the IP
address 225.2.100.1 is a multicast IP address.
- What is a broadcast IP address?
The datagram with a broadcast IP address is received and processed by all the
hosts in the local network. For example, the IP addresses 255.255.255.255,
192.9.205.255, 180.10.255.255, 10.255.255.255 are broadcast IP addresses.
- How IP addresses are classified?
IP addresses are classified based on the number of bytes allocated to the
Network ID and the Host ID in an IP address.
- What is the use of classifying IP addresses?
IP addresses are classified so that networks and hosts can be easily managed.
- What are the different classes of IP addresses?
IP addresses are classified into the following classes:
- Class A
- Class B
- Class C
- Class D
- Class E
- How to determine the class of an IP address?
The class of an IP address can be determined from the first four bits of the
first byte of the IP address.
- How many bytes does each Class of IP address use to represent network and host IDs?
The number of bytes used by each network Class to represent the network and
host are shown below:
+----------+----------------+----------------+
|IP Address| Bytes used for | Bytes used for |
|Class | Network ID | Host ID |
+----------+----------------+----------------+
| Class A | 1 | 3 |
| Class B | 2 | 2 |
| Class C | 3 | 1 |
| Class D | - | - |
| Class E | - | - |
+----------+----------------+----------------+
- What is the format of the various IP address classes?
The format of the different IP address classes is shown below:
+----------+-------------------------------------+
|IP Address| IP Address format |
|Class | |
+----------+-------------------------------------+
| Class A | 0NNNNNNN.HHHHHHHH.HHHHHHHH.HHHHHHHH |
| Class B | 10NNNNNN.NNNNNNNN.HHHHHHHH.HHHHHHHH |
| Class C | 110NNNNN.NNNNNNNN.NNNNNNNN.HHHHHHHH |
| Class D | 1110MMMM.MMMMMMMM.MMMMMMMM.MMMMMMMM |
| Class E | 1111RRRR.RRRRRRRR.RRRRRRRR.RRRRRRRR |
+----------+-------------------------------------+
In the above table,
N denotes the network ID bits,
H denotes the host ID bits,
M denotes the multicast address bits and
R denotes reserved bits.
- How many number of networks and hosts can be represented using the IP address classes?
The maximum number of networks and hosts that can be represented using the
various IP address classes is shown below in the table:
+----------+----------------+---------------------+
|IP Address| Maximum number | Maximum number of |
|Class | of networks | hosts per network |
+----------+----------------+---------------------+
| Class A | 126 (2^7 - 2) | 16777214 (2^24 - 2) |
| Class B | 16384 (2^14) | 65534 (2^16 - 2) |
| Class C | 2097152 (2^21) | 254 (2^8 - 2) |
| Class D | - | - |
| Class E | - | - |
+----------+----------------+---------------------+
In the above table,
- The numbers are calculated using the number of bits used to represent the
network ID and host ID.
- The maximum number of networks for Class A IP address is reduced by 2 to
account for the reserved network IP address 0.xxx.xxx.xxx and 127.xxx.xxx.xxx
- The maximum number of hosts for all the classes is reduced by 2 to account
for the reserved host IP address in which all the host ID address bits are
either one or zero.
- What is the possible range of IP addresses for the different classes?
+----------+-----------------------------------+
|IP Address| Possible range of IP address |
|Class | |
+----------+-----------------------------------+
| Class A | 0.0.0.0 through 127.255.255.255 |
| Class B | 128.0.0.0 through 191.255.255.255 |
| Class C | 192.0.0.0 through 223.255.255.255 |
| Class D | 224.0.0.0 through 239.255.255.255 |
| Class E | 240.0.0.0 through 247.255.255.255 |
+----------+-----------------------------------+
- What kind of networks use a Class A or Class B or Class C IP address typically?
Class A IP address is used for a network with large number of hosts. Class C
IP address is used for a network with less number of hosts. Class B IP address
is used for a network with medium number of hosts.
- What is the use of Class D IP addresses?
The Class D IP addresses are used for multicasting.
- What is the use of Class E IP addresses?
The Class E IP addresses are reserved for experimental purpose.
- How to decide which class of IP address to use for a particular network?
The class of IP address to use for a particular network depends on the maximum
number of hosts in the network. For example, if the maximum number of hosts in
a network will be less than 254 hosts, then a Class C IP address can be used
for the network. If the maximum number of hosts in a network will be greater
than 254 hosts but less than 65534, then a Class B network can be used.
- Does the maximum number of hosts in a network, restrict the class of IP address that can be used for the network?
No. Any possible class of IP address can be used to represent a network. For
example, if a network has 200 hosts, it can use either a class A or class B or
class C IP address.
- What are the various special IP addresses?
The various special IP address are shown below in the table:
+----------------+-------------------------------------------------+
|IP Address | Description |
+----------------+-------------------------------------------------+
|0.0.0.0 | Local host. |
+----------------+-------------------------------------------------+
|127.xxx.xxx.xxx | Local loopback address. The value of the last |
| | 3 bytes are ignored. The datagram with this IP |
| | address is never transmitted over the network. |
+----------------+-------------------------------------------------+
|xxx.0.0.0 | Local host IP address. The x represents the |
|xxx.xxx.0.0 | network ID bits. |
|xxx.xxx.xxx.0 | |
+----------------+-------------------------------------------------+
|0.xxx.xxx.xxx | IP address of a host in the local network. The |
|0.0.xxx.xxx | x represents the host ID bits. |
|0.0.0.xxx | |
+----------------+-------------------------------------------------+
|255.255.255.255 | Limited Broadcast address. Datagram with this |
| | address will be received and processed by all |
| | the hosts in the local network. This datagram |
| | is not forwarded to other networks by routers. |
+----------------+-------------------------------------------------+
|xxx.255.255.255 | Directed broadcast address. The datagram with |
|xxx.xxx.255.255 | this IP address is received by all the hosts in |
|xxx.xxx.xxx.255 | the specified network. The x represents the |
| | network ID bits. |
+----------------+-------------------------------------------------+