Host naming and addressing on networks

Network hosts and PC's are identified by their names or from their network addresses. The term network addressing refers to the method of identifying the network, and hosts located on the network. Different networking protocols use different methods to address the networks and hosts. These are:.

TCP/IP addressing.

Hosts located in a TCP/IP network follow the IP addressing scheme. The IP address is made up from 32 bits composed of 4 sets of 8 bytes (called an octet) each. They are expressed as decimal numbers separated by a decimal point or full stop. The notation. 192.168.1.100 is an example of an IP address. IP addresses can then further be divided into public (registered) or private (unregistered) addresses. Organizations that use public addresses can be connected directly to the Internet while the private IP addresses can only be used inside one of those public networks. IP addresses are classified into classes A, B, C, D, and E. Only the addresses from the classes A, B and C are assigned to commercial and non commercial organizations, and are known as Classful IP Addresses.

The first byte of any IP address identifies the class of the IP address which is used in the network. For example, a host with an IP address 92.128.0.10 is using a class A IP address and a host with an IP address 192.170.200.10 is using a class C IP address. A second 32-bit number, known as subnet mask, is also used to help identify the network address from the host address. When the address is converted to a binary number, the network part is given a binary value of 1 and then the host part is given a value of 0 in the subnet mask.

For example, if the subnet mask was 255.255.0.0, the first 16 bits of the IP address would represent the network address and the last 16 bits would then represent the host address. It can be sometimes very complicated to understand this, so to help you should study at least a basic overview of binary mathematics to help.

Classful subnetting.

Sub netting happens when the process of two or more networks are created in segments by using the host portion of the IP address. Sub netting creates multiple broadcast domains to help reduce the broadcast traffic and also allows administrators to effectively manage the IP address range. It also allows increased security on the network and helps contain network traffic to local area network segments.

A network with a class C IP address of 192.168.2.0. Which has the default subnet mask of 255.255.255.0, can have only one large network segment with 254 hosts. If you then use some bits from the host portion, you can also create two, three, or even four segments. But when the number of segments increase, the number of hosts in each of the segments is reduced.

IPX addressing.

A NetWare network environment, has only the servers with assigned hostnames. These names are made from a maximum of 47 characters. The clients don't have any hostnames and they use their IPX addresses to identify them on the network. NetWare networks are assigned a 32-bit hexadecimal address. The servers and also the workstations use a 48-bit hexadecimal address. This is made up from the the MAC address of the network interface card.

This address is appended to the network address to create a unique node address to identify the PC on the network.

The following is an example of an IPX address:

0AC74F02:01255F99AA48

The first part of the IPX network address is the address of the logical network, and then the second part is the unique MAC address on the network interface card. If there are any zeros at the start, they are not included. The IPX address can also be written as groups of four hexadecimal numbers separated by colons. The above address can thus be written as:

AC7:4F02:0125:5F99:AA48

NetBEUI addressing.

The NetBEUI network protocol uses a NetBIOS naming convention to address the computers in a network. NetBIOS computer names are made from a maximum of 15 characters such as a Server1, Workstation1, and so on.

NetBEUI uses 3 methods to resolve NetBIOS computer names to IP addresses, these are:

Broadcasting

If the host doesn't have the IP address of a NetBIOS host in its cache memory, then it broadcasts the NetBIOS name to the entire network.

LMHOSTS file

This is a text file used to map the IP addresses to the NetBIOS computer names.

NBNS

This is the NetBIOS Name Server (also known as the WINS server) which maps NetBIOS names to IP addresses. Since the NetBIOS name resolution can mainly depend on broadcasts, the NetBEUI protocol creates huge amounts of network traffic, especially when there are large numbers of computers on a network.

Automatic Private IP Addressing (APIPA).

This is the default configuration used on most TCP/IP based operating systems to dynamically obtain an IP address configuration from the Dynamic Host Configuration Protocol (DHCP) server. When the DHCP server is unavailable, the computer will assign itself an IP address automatically. This address will be in the range of 169.254.0.0 to 169.254.255.255 and a subnet maskof 255.255.0.0.

With an APIPA address, the computers can connect only to other computers with an APIPA address on the local network segment, If a PC has been configured to obtain its IP address from a DHCP server, but it does not support APIPA, its IP address automatically defaults to 0.0.0.0.

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