How to configure an Ethernet Network Device in Ubuntu
Ethernet is one of the oldest and most established network technologies. When we talk of Ethernet, we refer to wired networks - all the computers on the network are connected by cabling to a central hub or router.
You might go online via Ethernet in a variety of situations. If you have DSL or cable broadband service at your home or workplace, for example, you might use a DSL router that has a number of Ethernet ports. Your computer will then connect to this router via an Ethernet cable.
If you're running Ubuntu on a PC in an office environment, it's likely that you will connect to the local area network using Ethernet. This lets your computer communicate with other computers, as well as with shared printers. In some offices in which an Internet connection is provided, this connection might also allow you to go online.
In most cases, NetworkManager's roaming mode will sense a wired Ethernet connection and automatically connect using the Dynamic Host Control Protocol (DHCP). This means that your computer receives its IP address, gateway, subnet mask, and Domain Name System (DNS) addresses automatically. All routers manufactured today are set up to automatically use DHCP out of the box.
If you need to manually specify network details such as IP and router addresses, perhaps because you work in an office environment with nonstandard systems, start by speaking to your system administrator or technical support person to determine the settings you need. Ask the administrator for your IP address, DNS server addresses (there are usually two or three of these), your subnet mask, and the router address (sometimes referred to as the gateway address). The settings you will get from your system administrator will usually be in the form of a series of four numbers separated by dots, something like 192.168.0.233. After you have this information, follow these steps:
1) Click the NetworkManager icon in the notification area, and then select Manual
Configuration.
2) Click the Unlock button in the dialog box that appears. Supply your password when prompted, and then click the Authenticate button.
3) Find your network device in the list. It should be referred to as Wired Connection. Click its entry, and then click Properties.
4) In the dialog box that appears, uncheck the Enable Roaming Mode check box. This overrides NetworkManager's capability to automatically manage the device and allows you to manually configure the device. In the Configuration drop-down list, make sure Static IP Address is highlighted. In the IP Address, Subnet Mask, and Gateway Address text boxes, fill in the relevant details. Figure 8-2 shows an example of these settings. Click OK after filling in the information.
5) Click the DNS tab in the Network Settings dialog box.
6) Click the Add button, and then type the first DNS address. Press Enter when you've finished. Click Add again, and enter the second DNS address, if you have been given one, and then enter a third if you were given one.
7) Click the Close button.
Your network connection should now work. If you find it isn't working, try rebooting.
Tips & Tricks
TIP: If a DHCP server is not available, Ubuntu will attempt to set up a network automatically using the Zeroconf (or Zero Configuration Networking) system, just like Microsoft Windows systems. (Microsoft refers to this as Automatic Private IP Addressing, but it's also known as link-local.) In other words, if a bunch of computers plug into a hub or router on an ad hoc basis, without being configured and without a DHCP server operating, they will be able to network with each other. To make this work, each computer randomly assigns itself a unique IP address that starts with 169.254 with a subnet mask of 255.255.0.0.
TIP: If you're using a static IP address with a router, such as that provided by a DSL modem, the DNS address will probably be the same as the router/gateway address.
Tags: boot,dhcp,ethernet,modem,network,share
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