Question

Explain the two ways to give a computer an IP address, subnet mask, and default gateway.

Answer 1

To give acomputer an IP address, there are two ways,

-using DHCP – automatic assignment of IP addresses

In a home network, the router usually decides how the LAN must work. The router will forward traffic between the clients on the LAN and also between LAN and the Internet.The router also hands out IP addresses and other necessary information to the computers on the network. This is done via DHCP, which stands for Dynamic Host Configuration Protocol. It is a protocol to automatically hand out configuration to computers and other devices on the network.

Usually when you receive your home router it is already pre-configured with a DHCP server to hand out configuration to your computers and other devices. The router is also prepared so that the addresses that the router hands out via DHCP is on the same IP network as the router’s LAN IP address. This is necessary for the clients to be able to use the router as their Default Gateway.

When a computer connects to a network it will try to ask for an IP address. This is done by sending out a DHCP request where it asks if there are any available DHCP servers on the network. If any DHCP server responds then the computer will use DHCP to ask for an IP address and all the other necessary information it needs from the DHCP server.So when your router sees this DHCP request it will hand out an available IP address from its pool of free IP addresses, together with the other details that the computer needs.

-Manual configuration of an IP address

Instead of letting the computer obtain its IP address from the router via DHCP you can choose to manually configure the IP settings on the computer. Normally this is avoided since it can cause a few different problems unless it is handled properly by the administrator

When you configure an IP address manually on a computer you need to configure the same settings that a computer normally receives via DHCP:

• An available IP address on the same IP network as the router
• The same Subnet Mask that the router is using
• Default Gateway, which should be set to the LAN IP address of the router
• DNS Server address – either the router LAN IP address or another DNS server on the Internet. You may use the same address that the router normally hands out via DHCP

Subnet:

Subnetting is the process of stealing bits from the HOST part of an IP address in order to divide the larger network into smaller sub-networks called subnets. After subnetting, we end up with NETWORK SUBNET HOST fields. We always reserve an IP address to identify the subnet and another one to identify the broadcast address within the subnet. In the following sections you will find out how all this is possible.

Imagine a network with a total of 256 addresses (a Class C network). One of these addresses is used to identify the network address and another one is used to identify the broadcast address on the network. Therefore, we are left with 254 addresses available for addressing hosts.

If we take all these addresses and divide them equally into 8 different subnets we still keep the total number of original addresses, but we have now split them into 8 subnets with 32 addresses in each. Each new subnet needs to dedicate 2 addresses for the subnet and broadcast address within the subnet.

The result is that we eventually come up with 8 subnets, each one possessing 30 addresses available for hosts. You can see that the total amount of addressable hosts is reduced (240 instead of 254) but better management of addressing space is gained.

subnetting can be done using  the Binary Method and then Using the host's formula.The host's formula will tell you how many hosts will be allowed on a network that has a certain subnet mask. The host's formula is 2n - 2. The "n" in the host's formula represents the number of 0s in the subnet mask, if the subnet mask were converted to binary

Default gateway:

A default gateway is used to allow devices from one network to communicate with devices in another network. It can be reffered as an intermediate device between the local network and the internet. It's necessary for transferring internal data out to the internet, and then back again.

So, the default gateway device passes traffic from the local subnet to devices on other subnets. The default gateway often connects the local network to the internet, although internal gateways for communication within a local network also exist.

Internet default gateways are typically one of two types:

• On home or small business networks with a broadband router to share the internet connection, the home router serves as the default gateway.
• On home or small business networks without a router, such as for residences with dial-up internet access, a router at the internet service provider location serves as the default gateway.

Default network gateways can also be configured using an ordinary computer instead of a router. These gateways use two network adapters where one is connected to the local subnet and the other is connected to the outside network.

Either routers or gateway computers can be used to network local subnets such as those in larger businesses.