Configure a network to use an IP addressing scheme
TCP/IP services 2
Dynamic Host Configuration Protocol (DHCP) 3
Windows Internet Naming Service (WINS) 6
Domain Name Service (DNS) 8
Installing and configuring TCP/IP 11
Manual configuration 11
Automatic configuration 12
TCP/IP tools 13
Summary 15
Check your progress 15
TCP/IP services
TCP/IP is the basic protocol of the Internet and is comprised of other protocols including UDP, ARP and ICMP. The TCP/IP protocol suite also provides a number of useful services, which include:
· Dynamic Host Configuration Protocol (DHCP)
· Windows Internet Naming Service (WINS)
· Domain Name Service (DNS)
· Hypertext Transfer Protocol (HTTP).
With all the new Windows operating systems TCP/IP is automatically installed during the installation of the operating system. You can choose to configure your computer with an IP address during the installation or wait until after the installation has been completed.
Dynamic Host Configuration Protocol (DHCP)
Dynamic Host Configuration Protocol (DHCP) enables the assignment of dynamic TCP/IP network addresses on a first come, first served basis, based on a specified pool of available addresses. An organisation may only have a limited number of IP addresses to be shared among the client computers. By configuring the DHCP server with a pool of IP addresses, these addresses can then be shared by the users within the organisation, thus simplifying IP address administration.
The client computer is configured to obtain an IP address automatically from a DHCP server. When the client machine starts up, the DHCP service assigns the next available TCP/IP address for the period of the lease, as configured on the server. The DHCP server can also be configured to assign the same IP address to a particular machine every time it starts up. The DHCP server service is installed and configured on a server computer.
Figure 1 below shows the configuration of an IP address scope on a DHCP server. Any computer starting up on this network will be allocated an IP address from the range 192.168.1.1 to 192.168.1.100.
Figure 1: IP address scope on a DHCP server
For a client computer to be allocated an IP address, you will need to check the option ‘Obtain an IP address automatically’ from the TCP/IP Properties window as can be seen in Figure 2.
Figure 2 below shows an example of how TCP/IP properties are configured for automatic assignment of an IP address on a client computer. To get to this screen on a Windows 2000 or XP computer, you will need to go to:
My Network Places / Local Area Connection, Properties / TCP/IP Properties.
Figure 2: Configuration for automatic assignment of an IP address on a client computer
Once you have chosen to obtain an IP address automatically, the Advanced TCP/IP Setting option will display that DHCP has been enabled on the client computer, as can be seen from Figure 3 below.
Figure 3: Advanced TCP/IP Settings show that DHCP has been enabled
Windows Internet Naming Service (WINS)
Windows Internet Naming Service (WINS) enables the resolution of computer names to IP addresses. When an operating system is first installed on a computer one of the tasks is to configure the computer with a unique name known as the NetBIOS name. The NetBIOS name can contain up to 15 characters, for example, ACCOUNTS1, or LEGAL or PHILLIP. The computer name must be unique and no two computers on the network can have the same name.
By having a unique name for each computer, an administrator or user on the network does not need to remember the IP address of the client computer. To communicate with another computer on the network you need only enter the name of the computer — the operating system does the rest.
WINS maintains a database on the server that accepts requests from Windows or DOS clients to register with a particular NetBIOS name. The server keeps track of which NetBIOS names are linked to which IP addresses. Because WINS manages the mappings between IP addresses and NetBIOS names, clients do not have to broadcast their NetBIOS names to the rest of the network. The elimination of this broadcast traffic improves network performance.
The WINS Server service is installed on a server computer; however, both a Windows server computer and a workstation can use the WINS server to resolve network names.
Figure 4 below shows how a user adds the IP address of the WINS server in the Advanced TCP/IP Settings window from the WINS tab.
Figure 4: IP address of WINS server added in the TCP/IP properties on the client computer
Domain Name Service (DNS)
The Domain Name Service (DNS) was introduced in 1984 when the Internet was a relatively small network established by the US Defence Department for research. DNS lets us use hierarchical, friendly names to easily locate computers and other resources on a TCP/IP network that contains data similar to the Yellow Pages.
DNS is a database that contains mappings of DNS domain names, such as ‘legal.forth.com’ to an IP address. DNS is a:
· mechanism for querying and updating the database
· mechanism for replicating information in the database among servers
· schema for the database.
The DNS is implemented as a hierarchical system including host names and domain names. The names in a DNS database form a hierarchical tree structure called the domain name space. Domain names have individual labels separated by stops or dots (.) for example: legal.forth.com.
A Fully Qualified Domain Name (FQDN) uniquely identifies where the host is located within the DNS hierarchical tree by specifying a list of names separated by dots on the path from the referenced host to the root server.
Figure 5 below shows an example of a DNS tree with a host called ‘legal’ within the ‘forth.com.’ domain. The FQDN for the host would be legal.forth.com.
Figure 5: An example of a DNS tree
The DNS service resolves computer names to IP addresses, such as resolving the computer name ‘legal.forth.com’ to the IP address 203.70.1.2.
Domain names must be registered with an Internet naming authority that works on behalf of the ICANN (Internet Corporation for Assigned Names and Numbers). ICANN has established conventions for the Top Level Domains (TLDs) that apply to every type of organisation that uses the Internet, an example of which can be seen in Table 1 below. Existing abbreviations are reserved for use by organisations, as well as two- and three-letter abbreviations used for countries.
Table 1: Criteria for domain name registration
DNS domain name / Type of organisationcom / Commercial organisations
edu / Educational institutions
org / Non-profit organisations
gov / Non-military government organisations
net / Networks (the backbone of the Internet)
mil / Military government organisations
arpa / Reverse DNS
xx / Two-letter country code for example:
.au for Australia / .jp for Japan / .ca for Canada
Accredited registrars carry out registration, and each country has its own controlling body. In Australia this is currently the Australian Domain Names Authority (AuDA), which accredits local registrars such as NetRegistry. Figure 6 below shows the IP address of the Domain Name Server configured on the client computer.
Figure 6: Domain Name Server configuration on a client computer
Installing and configuring TCP/IP
With most recent Windows operating systems the TCP/IP protocol is automatically installed during installation of the operating system. By default, the TCP/IP settings are set to ‘Obtain an IP Address Automatically’, that is, through a DHCP server.
If a DHCP server cannot be located by the workstation when it starts, the workstation will automatically be assigned an address from the range 169.254.0.1 to 169.254.255.254. This range is set aside by the Internet Assigned Numbers Authority (IANA) for this purpose. The workstation broadcasts its intended use of the randomly chosen address to ensure that no other workstation on the same network has chosen the same address.
You will need to determine if you will be manually configuring TCP/IP on your computer, or whether a DHCP server will assign IP addresses to all computers on the network.
Manual configuration
If you are required to manually configure your computer with an IP address, you will need to have the following information to hand:
· Your workstation’s IP address. This is the unique address that identifies a particular computer on a TCP/IP network. This consists of four numbers, separated by a dot, for example: 203.60.1.2.
· Your network’s subnet mask for each network adapter on the network. The subnet mask is a number mathematically applied to the IP address that determines the network that the computer belongs to. For example, given the subnet mask of 255.255.255.0 to the above IP address 203.60.1.2, the net ID is 203.60.1.0 and the host ID is 0.0.0.2.
· Your default gateway. The default gateway is a device that servers as a router. If a default gateway is not specified, the computer is unable to communicate with other devices outside its subnet, that is, outside its own network.
· The domain name server for the network. This is a computer that serves as an Internet host and performs translation of Fully Qualified Domain Names (FQDNs) into IP addresses.
Figure 7 shows manual configuration of an IP address, subnet mask, and default gateway with preferred and alternate DNS servers.
Figure 7: Manual configuration of an IP address, subnet mask, default gateway with preferred and alternate DNS servers
Automatic configuration
For automatic configuration, a user just needs to check the ‘Obtain an IP address automatically’ option in the Internet Protocol Properties window. The DHCP server will then configure all the information without any input from a user. The server will assign:
· an IP address
· subnet mask.
If an organisation has been assigned a range of IP addresses for use by staff, this range can be created as the scope for the DHCP server, accompanied by a subnet mask, default gateway, DNS and WINS, if they have been configured.
Figure 8 below shows the TCP/IP configuration information of the computer with a host name of G1C1. What information can you see from this screen?
Figure 8: TCP/IP configuration of the computer named G1C1
TCP/IP tools
Once TCP/IP has been configured, there are a few tools that can be used to check to see if TCP/IP has been configured correctly on your computer.
IPCONFIG/ALL command
As you can see from Figure 8 above, the command IPCONFIG/ALL displays all the current local TCP/IP configuration information, including:
· the host name
· MAC address of the network adapter as well as its brand and type
· whether this interface has been configured to use DHCP
· IP address of the host
· subnet mask
· default gateway
· DHCP server
· when an IP address was leased (obtained) and is due to expire.
PING
PING is a tool to determine the connectivity between two nodes. This command is used from the command line, and as you can see from Figure 9, you can use PING with the loopback address, 127.0.0.1 or the host’s own IP address. You can also PING any other valid address of a host, on this or any connected network.
Figure 9: The PING command
NSLOOKUP
NSLOOKUP is a tool to determine whether DNS has been successfully configured.
TRACERT
TRACERT displays the route taken by the Internet Control Message Protocol (ICMP) to a remote host.
NETSTAT
NETSTAT displays the current connectivity information such as port number and any connected ‘foreign’ IP address.
Summary
TCP/IP is automatically installed during the installation of most operating systems, by default. A Network Administrator can choose to manually configure a computer with a TCP/IP address or have several computers on a network assigned an IP address through a Dynamic Host Configuration Protocol (DHCP) server.
A range of IP addresses are configured within the scope of the DHCP server. The IP addresses are leased for a specific period of time.
Once TCP/IP has been configured on a computer, there are various tools that can be used to test the TCP/IP installation and configuration such as IPCONFIG and PING.
Check your progress
Now you should try and do the Practice activities in this topic. If you’ve already tried them, have another go and see if you can improve your responses.
When you feel ready, try the ‘Check your understanding’ activity in the Preview section of this topic. This will help you decide if you’re ready for assessment.
Reading: Configure a network to use an IP addressing scheme XXX
2005