This article will focus on mechanisms

Transcription

1 Network configuration In today s world networking (Internet access really) has become increasingly important aspect of computing since it has allowed people to communicate their thoughts in a relatively accessible, and inexpensive format and has has also given people a means through which to transfer inconceivable amounts of data reasonably seamlessly. This article will focus on mechanisms through which one can establish network connectivity and will deal with those issues that may not be able to be handled during the process of installing the operating system on your system. A quick primer on network addressing If you re unfamiliar with computer networking in general here is a quick primer on how it works. Of course, you now have the option of wireless and wired connections. In the case of wired connections you generally have two options through which to organize your local network. One is through static addressing and the other is dynamic addressing. In the case of static addressing a computer is given an address that stays the same over time. In the case of dynamic addressing a computer is given a new address each time the system starts or a certain time period is exceeded. This second style of addressing is also sometimes referred to as DHCP addressing. Within these two types of addressing there are certain classes of addresses which can be used in order to delineate between computers on a local network and those that are connected to the Internet. For instance, a class C network is normally connected to a small number of systems, a class B network is connected to a larger number of computers while a class A network is connected to the Internet. The addressing scheme for these networks is as follows for IPv4 networks. Useful links: t_ipaddressclassabandcnetworkan dhostcapacities.htm Classful_network The easiest way to work out whether your network is using static or dynamic addressing is to hop on another computer in the network and right clicking on the relevant network interface connection in the network control panel applet (on a Windows machine). Then right click, on Internet Protocol (TCP/IP). If the Obtain an IP address automatically option is selected then obviously you are using DHCP. If the Use the following IP address option is selected then you will obviously be using static IP addressing. Figure 1. How to determine what style of addressing is applicable to your local network 21

2 Figure 2. Configuration of a wired connection using DHCP via the NetworkManager You should be able to work out what style of addressing your using on a late Linux box by using the information provided in the rest of this article. Another option is to just call your local networking guru or local system administrator. Wired connection A wired connection is important for two reasons. Firstly, it allows people to connect other computers within their own network. Secondly, in the vast majority of cases it also allows them to share an Internet connection through either a router, modem, or some form of gateway (which can take the form of another Fedora system or even a Windows system which has Internet Sharing enabled ). You should be able to setup/ configure your network device by following steps while in the GNOME desktop environment. Firstly go to, System > Administration > Network. Select relevant interface (it will be listed as an Ethernet device in the NetworkManager). Then click on the Edit button. You ll be given the option of selecting from being able to automatically obtain an IP address using a DHCP or statically assigning an address. Please select the former. Click OK Figure 3. Configuration of a wired connection using DHCP via the command line Configuration and click the Activate button in order to bring up the interface. Another way in which to configure your network interface is using the command line. Firstly open up a command terminal by hitting [Alt] + [F2]. Type in gnometerminal and then hit the Run button. This should bring up a window with a prompt. Type in ifconfig -a and hit [Enter]. This will give you a listing of all available network interfaces (all network cards) installed on your system. Based on the network card that you then wish to utilize you can then run the ifup command along with the name of the interface card in order to assign an IP address to your network interface card. For example, let s say your network interface card is called eth0 you just run ifup eth0 from the command line. Thereafter, you will be assigned a network address (assuming you have a DHCP server, router, firewall on your local network). Funnily enough, the second means of configuring your network interface is the actual method which the GUI front end uses to setup your network card. with a static IP address Setting up or configuring your network device to use network device to use static IP addressing is slightly more complicated than using a dynamically allocated IP addressing. However, by following steps while in the GNOME desktop environment. Firstly go to, System > Administration > Network. Select relevant interface (it will be listed as an Ethernet device in the NetworkManager). Then click on the Edit button. You ll be given the option of selecting from being able to automatically obtain an IP address using a DHCP or statically assigning an address. Please select the latter and enter an IP address, subnet mask, and if necessary a gateway (namely, a computer through which your Fedora machine will use to access the rest of the world ). Click OK and click the 22 LINUX IDENTITY Pack

3 Activate button in order to bring up the interface. Another way in which to configure your network interface is using the command line. Firstly open up a command terminal by hitting [Alt] + [F2]. Type in gnometerminal and then hit the Run button. This should bring up a window with a prompt. Type in ifconfig -a and hit [Enter]. This will give you a listing of all available network interfaces (all network cards) installed on your system. Based on the network card that you then wish to utilize you can then run the ifconfig command along with the name of the interface card in order to assign an IP address to your network interface card. For example, let s say your network interface card is called eth0 you just run ifconfig eth from the command line. Funnily enough, the second means of configuring your network interface is the actual method which the GUI front end uses to setup your network card. Wireless connection As was the case with other hardware driver support. Wireless support has come a very long way since wireless technology was first introduced. Only a few years ago, one had to download firmware and even resort to using Windows drivers in an emulated environment using NDISWrapper, wrapper.sourceforge.net/joomla/ in order to get wireless working. Nowadays, quite a few wireless cards are supported out of the box ( Figure 4. Configuration of a wired connection using static addressing via the NetworkManager Even so, for some strange reason wireless connectivity doesn t seem to be automatically added to your network profile at startup. As such, you must manually create the device and add it to your profile in the NetworkManager. Firstly go to, System > Administration > Network. Then hit the New button and elect to add a new Wireless Device. Keep on hitting the forward button until you have finally added a new Wireless device to the NetworkManager. Keep in mind that the information regarding what type of network you have setup will naturally be dependent on the type of Network that you wish to connect to. For example, Ad-Hoc mode could be used when there is no access point available and you just want to put together a very simple network. Managed mode, should be used when there are many access points available and you just want to connect to any one of them. In Master mode, your computer will obviously act as an Access Point. Auto mode will obviously attempt to automatically determine what the correct settings are. Thereafter, a little icon should pop up in your taskbar asking whether you would like to connect to your local network. Oddly enough, this wasn t to be the case Intel net/ Atheros news/linux.html projects/madwifi/ Figure 5. Wireless configuration via NetworkManager 23

4 Figure 6. How to configure a xdsl connection for my own attempts at wireless connectivity. While I was able to find my local access point it didn t seem as though I was able to successfully get an IP address from my Linksys WRT54GL Access point. Even more strange though was the fact that my attempts at using the wireless button to turn it on and off resulted in Kernel oopses. Hopefully, they ll get this fixed by the time the release candidate is due. A good overview of how things should work is available here: magazine/003jan05/features/ networkmanager/, with successful snapshots of a wireless setup available here, mediawiki/index. php/setup_your_ wireless_client_at_home. with an USB modem Several years ago configuring a DSL based USB modem via Linux was a harrowing experience. While it can still remain difficult it has become significantly easier. The main reason why this is the case, is that most manufacturers have become more open with regards to releasing information information regarding their hardware which has allowed for far quicker and accurate development of relevant drivers. If you are lucky and your particular modem is supported then you will not have to deal with downloading specialised drivers/firmware in order to get your modem up and running (such as the Alcatel Speedtouch ( faq/index.html)). In this case, all you have to do is run a xdsl client and follow the instructions provided by your ISP. In the case of Fedora the only available client in the default respository (at the time of writing) is Roaring Penguin, (also known as rp-pppoe). Most of the information on how to configure this particular piece of software is available in, /usr/share/doc/rp-pppoe-3.8. More information is available in the DSL-HOWTO, HOWTO/DSL-HOWTO/configure. html. The easiest way to configure it though is via the NetworkManager. Essentially, all you have to do is create a new xdsl connection, enter in the relevant details and Activate the connection. with an analog modem Even though it is slowly fading out of relevance as broadband and wireless technologies begin to dominate the networking landscape, dial up modems continue to remain a part of our Configuration networking landscape due to the pervasiveness of telephone connections. As long as your modem is supported under Fedora it should be quite easy to establish a connection to your local ISP. First step is installing the gnome-ppp package. Then go to Applications > Internet > Gnome-PPP. Enter the relevant details provided to you by your ISP and you should be ready to go. Probably the only real reason you would bother to make any changes to the default configuration would be to alter the Auto reconnect settings (your modem will attempt to re-establish your connection after your connection is dropped due to). Obviously, these settings can be accessed by hitting the Setup button and then checking the relevant checkbox in the Options tab. Sharing an Internet To have Windows setup as your gateway, go to Start > Windows > Control Panel > Network s. Thereafter, right click on the relevant network interface card. Hit the Advanced tab, then check the Allow other network users to connect through this computer s Internet connection option. Hit the OK button and then restart. Note that while your at it, you should probably enable the Firewall as well if you have not already done so in the latter parts of this magazine. Thereafter, just set your Fedora box to be configured via dynamic addressing and your Internet connection sharing should just work. Nonetheless, if you find that you re having trouble resolving URL s then you should try adding the IP addresses of your ISP DNS section of the NetworkManager. Moreover, in order to achieve name resolution you can also manually edit your /etc/resolv.conf file and adding your the relevant name servers in there (just open up the file using a text editor such as Gedit and then add a line which 24 LINUX IDENTITY Pack

5 reads nameserver [IP Address] ). More often than not though, these name servers are automatically assigned and configured to your system when you connect to your ISP via a DHCP broadband connection. Funnily enough, you can also set your Fedora system as a gateway to the Internet and allow all local traffic to be routed through that system or you can have a Windows system connected directly to the Internet with your Fedora system acting as a client of this machine. It can be a little bit involved though and there doesn t seem to be a good GUI based interface that was included in the default installation. A good guide is available here though, The reason why this may be the case is probably because in most cases nowadays a router/ firewall device may be already present on your network which means that all you may need to do is merely connect your system to the router/firewall via a patch network cable and things should be automatically setup since the DHCP server and all other configuration is handled by that device (all you need to do is to setup your network cards to be automatically be assigned an IP address via the Network- Manager). More details on how to setup your network router/ firewall as a DHCP server should be included in the user documentation. A good general overview of how it should work is included here, compnetworking.about.com/ od/homenetworking/ht/ routerconfigure.htm. Figure 7. Setup of GNOME-PPP Troubleshooting One of the biggest problems with computer networking is that there are many variables that you must deal with. If you ve found out that your computer is has been assigned with an IP address but is still unable to connect to other systems within your local network make sure to check that they have not been blocking you via a firewall, that they actually have a service that you can connect to (such as a Windows File Sharing or FTP access), and that you actually have the correct subnet mask attached to your network interface cards (they should be the same across all computers within the same network). 9 Conclusion Even though everyone uses the same computer virtually all the time it is inherently clear that we are becoming ever more reliant on network connectivity in order to get our work done (especially through Internet connectivity). Hopefully this article would have aided you in establishing this. Figure 8. Shows the web based console interface for my local Linksys firewall/router which is currently setup to act as a DHCP server 25