Obtaining your Network information during Linux Integration

Before you can connect to a TCP/IP^[1] network, you need to know your:

1. IP address
2. Subnet
3. Netmask
4. Gateway

If you are connecting to an existing, administered network, then the administrator will provide this information. Otherwise, you need to decide on an addressing scheme yourself.

An IP address^[2] uniquely identifies a host in a TCP/IP network with a 32-bit^[3] number. Your computer's IP address can be assigned in several ways:

1. Statically
2. Dynamically with DHCP
3. Dynamically with BOOTP

You need to decide whether to assign your IP address statically or dynamically. Use a statically assigned IP address if the machine needs a fixed address. For example, computer labs and offices with permanent installations usually use static IP addresses for simplicity. Use DHCP or BOOTP when your network server assigns IP addresses automatically.

• Subnets and Routing: Computers on the same subnet^[4] communicate directly, without the need for routing.^[5] The computers label data with destination and return addresses and send it to the subnet. Each host on the subnet inspects the data, but only the intended recipient reads the data; the other hosts ignore it.

When computers send information from one subnet to another, they send the data through a router. That subnet, in turn, hands the data off to another router, which sends the data to the next subnet, until the data reaches its destination. This all works a little like the Post Office. Computers send data through routers, acting like a post office for two neighborhoods.

• Gateway and Netmask: The departure and entry point to your network is called the gateway, which is usually a router on the network that directs traffic into and out of your subnet. The gateway can derive the destination subnet from the destination IP address using a netmask^[6]. If you know your IP address and netmask, you can easily find your subnet. The following series of images examines netmasks.

Subnet: A portion of a network that shares a common address component. On TCP/IP networks, subnets are defined as all devices whose IP addresses have the same prefix. For example, all devices with IP addresses that start with 100.100.100. would be part of the same subnet.
Dividing a network into subnets is useful for both security and performance reasons. IP networks are divided using a subnet mask.
Gateway: A gateway is a network point that acts as an entrance to another network. On the Internet, a node or stopping point can be either a gateway node or a host (end-point) node. Both the computers of Internet users and the computers that serve pages to users are host nodes. The computers that control traffic within your company's network or at your local Internet service provider (ISP) are gateway nodes. Can transcode or allow different protocols to talk to each other.
You need to provide Linux with your netmask so it knows its subnet address. When your computer has a data packet whose destination subnet address is not the same as its own, it sends the packet to the gateway. If the destination computer is on the same subnet (and so shares the same subnet address) there is no need to send it through a gateway. In the next lesson, you will configure a network connection using netcfg.

This page matches the required network parameters with their descriptions. Below are the results.

1. DHCP: A protocol that assigns IP addresses dynamically
2. Static: Specifies an IP address stored on the host for continual use
3. Gateway: Host on a subnet configured to communicate with other networks
4. Netmask: A 32-bit number determining the size of the subnet portion of the address
5. Subnet: A group of computers that send data to each other without the need for routing

• Using Dynamic Host Configuration Protocol:
  Setting up a Dynamic Host Configuration Protocol (DHCP) server allows you to centrally manage the addresses and other network information for client computers on your private network. With DHCP configured on your network, a client computer can simply indicate that it wants to use DHCP and the DHCP server can provide its
  1. IP address,
  2. network mask,
  3. DNS server,
  4. NetBIOS server,
  5. router (gateway),
  and additional information needed to communicate on the network. With DHCP, you can greatly simplify initial network configuration that each client computer on your network needs to do. Later, as your network evolves, you can easily update that information, having changes automatically picked up by clients when they restart their network interfaces. Assuming you have already set up the physical connections between your DHCP server and the client computers on your network (presumably an Ethernet LAN), the minimum you need to get the DHCP server working are:
  1. A configured /etc/dhcpd.conf file
  2. A running dhcpd server daemon (which can be started at boot time)
  After the DHCP server is running, it broadcasts its availability as a DHCP server to the LAN. A client simply boots up (with a Ethernet network interface turned on and DHCP identified as its method of getting network addresses), and the information it needs to get up and running on the network is fed to it from the server. The following sections describe how to set up your /etc/dhcpd.conf file, start the DHCP server, and configure DHCP clients.

[1] TCP/IP: Set of protocols that facilitate controlling the transmission of packets of information.

[2] IP address: A set of numbers that is a unique label for that interface on the network. It is represented by the notation X.X.X.X, where each X is a decimal number from 0 to 255.

[3] 32-bit: A number that has 32 binary digits. 32-bit IP addresses are written as four numbers separated by dots, X.X.X.X, where each number is in the range 0 to 255. Think of it as a string of 32 1's and 0's.

[4]Subnet: A set of machines that communicate without the assistance of a router. Networks and subnets are connected with routers to make larger networks.

[5] Routing: Subnets communicate through routers, so that only messages intended for a subnet's hosts are received. Without routing, data must be sent to every connected host, a very inefficient practice in large networks.

[6] Netmask: A set of numbers which indicates the network class. When its binary representation is anded with an interface IP address, the result is the network address.