1 Networking: A Beginner's Guide Course Content Introduction What is a LAN? What equipment is necessary for a LAN? Physical Network Setup Quick Way to Configure DSL Modem in Bridge Mode IP Logical Network Design Router Configuration DHCP DMZ and Port Forwarding Making Sure TCP/IP Works How to Connect 2 Computers Directly Using Crossover Cable Quick Way to Configure IP Address and Network Information in Windows 7 Manual IP Assigning IP Assigned by DHCP server Configuring IP Address and Network Information in Windows Vista How to Set IP Address and Network Information in Windows XP How to differentiate straight and crossover cable Troubleshooting Network Problem: Cannot Connect to Wireless Network? Using Ping to Troubleshoot Network Problem Using WinSockFix to Fix Windows XP Networking Problem 2 Introduction With computers getting cheaper and cheaper these days, it is not uncommon for a household to have more than one PC. If that describes you, then you have probably found yourself in the situation where you wished you could access the other PC to retrieve a file, use the printer attached to the other PC, play multi-player computer games, or most importantly share your broadband Internet access such as cable or DSL modem with the other PC. To accomplish this all you need is a home network where you connect two or more PCs What is a LAN? LAN stands for “Local Area Network.” Basically, it is a communications link between two or more computers to share information with each other. Although “Local Area” seemingly implies that LANs are always small, this is not always the case. A LAN could possibly consist of thousands of computers provided that they are all connected through the same network connection and are directly linked through hubs and switches. However, once a router becomes involved, the definition of LAN no longer truly applies and you may call a computer connected to another through a router a member of an Internetwork, or if it is part of the main Internetwork, the Internet, and a computer connected to the Internet. The Internet in general can be thought of as a great LAN with all of its members indirectly connected in a giant mesh with each other. 3 It is important to understand a bit about Networking in order to actually “build” or put together a Local Area Network. Every member of a network possesses an IP address, or a unique identifier of that computer which no other computer or node of the network can use. When a dial-up user connects to the Internet, he or she is either in use of or is dynamically assigned an IP address, which follows the following structure: xxx.xxx.xxx.xxx …Where each “xxx” is a three digit number from 0 to 254. For example, 163.56.52.199 is a valid IP address, while 53.275.41.3 is not, because 275 is above 254, which is the range of an IP address. This number is used on the Internet to specifically identify your computer. However, within a network, you use a special type of IP address. Although this is certainly not the correct terminology, I will refer to this as the “Internal IP” in this guide. I call it this because the Internal IP uses a special format: 192.168.xxx.xxx [most common in LAN's] or 10.xxx.xxx.xxx [common in large LAN's] or 4 172.16.xxx.xxx – 172.31.xxx.xxx [uncommon] Each of these Internal IP blocks, or groups of addresses, is specifically reserved for Internal IP addresses. What exactly is an Internal IP address? An Internal IP address is the IP address that a computer uses to communicate with other computers or nodes in a network. Think of it as the Office of the President. In the White House, there are many personnel that operate inside of it. However, there is only one true outlet – the President and his PR team. In this metaphor, each of the computers in the network is a member of the personnel of the White House. Amongst each other, they are free to communicate and all have (somewhat) of their own identity and voice. To the rest of the world (the Internet), however, your computer and all of the others in your network are represented through your WAN Address, or the IP address assigned to you by your Internet Service Provider. In other words, Juan, Joe, and Mike may have the Internal IP addresses 192.168.1.5, 192.168.1.77. and 192.168.1.83; however, when they surf the Internet, they are always represented as their WAN Address 24.54.51.146. 5 What equipment is necessary for a LAN? There are some basic equipment needs for a Local Area Network. These include the communication cards to connect the network plugs into (known as Network Interface Cards, or NICs), the cables to connect between nodes (known as CAT5 cables), the switch to connect all of the nodes to, and the router to connect the switch to the Internet (therefore, indirectly connecting each of the nodes to the Internet). Note that the switch and router are often combined in to a single unit these days. 6 For the most part, choosing a NIC is rather simple. In many cases your computer or motherboard may already possess one. However, in the case that you need to purchase a NIC, buy a cheap 10/100 NIC (you can find one at many retail outlets for under $20.00) or a nicer 10/100/1000 NIC. The only reason you would possibly want a 10/100/1000 NIC is if you planned on buying one to keep for more than a year or so, and are anticipating your own purchase of a gigabit switch. I would recommend buying a 10/100/1000 NIC if you can, but 10/100 would of course suffice in most circumstances. Cabling is never a serious issue these days. Just be smart enough to buy one that you know is right for your location (i.e. a five-foot cord won’t suffice in most circumstances, whereas a 1000- foot monster may not be such a great idea for your home LAN). The main issue at hand is the switch/router. I say this because there are many switch-router combinations each with their own merits. However, for the value, I would highly recommend the Gigafast or Netgear line of products appropriate for your network size. Something that you must understand is that networks have very little to do in physical configuration and almost everything to do with software and settings. Every switch/router has its own configuration software that is usually based off of the HTTP protocol (or in other words, accessed through a web browser). So, depending on the switch/router you choose, the configuration software for that switch/router will vary. Building The Network The most common home network is Ethernet, it’s a very popular LAN (Local Area Network) technology due to it’s inexpensive setup cost and reasonably fast speed. The other types of network are Token Ring, LocalTalk, and FDDI. The speed (data transfer rate) of an Ethernet can be 10Mbps (Ethernet), 100Mbps (Fast Ethernet) and 1000Mbps (Gigabit Ethernet). Mbps is called Megabits per seconds. From my opinion, 100Mbps speed might be sufficient for your network needs. There is one rule here, make sure all your network devices (router, network card, switch, hub, network cable) are able to support the network with particular speed (10Mbps, 100Mbps, 1000Mbps) which you plan to set up. If you plan to set up a Gigabit Ethernet, although you have 100Mbps' network card, but your router can only support 100Mbps, then the network speed would be 100Mbps. 7 Here is typical network topology Physical Network Setup 8 Ok, for your home network, it’s time to do some exercises, here is how I do physical network setup. I will use D-Link's DI-604 broadband router as an example. You can use other type of router according to your needs. Please prepare some straight network cable as well. Connect the WAN port on router to your cable/DSL modem using straight cable, then connect computers’ network card to router’s LAN ports using straight cable also. You can connect up to 4 computers to this router. Power on the router after finish connecting, you should be able to see the WAN and LAN lights on the router. Also you need to ensure that your DSL/Cable modem is configured in bridge mode, so that it can work well after connecting to router. Quick Way to Configure DSL Modem in Bridge Mode This briefly explains how to configure DSL modem in bridge mode from a computer, so that the computer can access to Internet by using dialer. This is very common setup after you have subscribed new DSL broadband service, you just need to configure the modem as a bridge, and after that configure PPPoE dialer in Microsoft Windows by providing username/password or other network information for accessing Internet. If you plan to connect the modem to router and set up a home network, you must set bridge mode on modem too. Here is the way we configure the DSL modem: 1) Connect DSL modem’s LAN port to computer’s network card by using straight through network cable. 9 2) Read the modem manual, find out the default modem IP address, after that you need to set computer with the IP address in same network with modem, so you can access and configure it. As an example, if the modem IP is 192.168.1.1, I set computer IP as 192.168.1.10 (you can set 192.168.1.X, X= number between 2 and 254), netmask as 255.255.255.0 and gateway as 192.168.1.1. 3) Open a web browser and key in http://DSL-modem-default-IP (example: http://192.168.1.1) into the address bar, after that hit Enter key. 4) The modem logon screen will appear, type in default username and password you found in modem manual. You will then log on to the modem management page. 5) Go to the correct configuration page by referring to modem manual, and then set the operation mode to Bridge mode. Here is an example: 6) The other important info for modem to work well is Virtual Path Identifier (VPI) and Virtual Circuit Identifier (VCI), you need to set these numbers correctly. If you get the modem from ISP, most likely it’s been pre-configured correctly. If you are not sure, have a look on common VPI and VCI used by different ISPs. Here is an example: 7) Ok, at this stage you have done the modem configuration, you can then proceed to configure PPPoE dialer on connected computer. or wired), you can then proceed to configure that wireless router or Ethernet wired router. . 10 After setting up the network, we need to decide what IP addresses need to be used for router and computers. IP Logical Network Design IP logical network design! This is one of the task which you need to do is do after you have decided to set up a network (wired or wireless) at home. This is the process to decide the IP addresses, netmask for your computers, router and other network devices. Since each IP address assigned to your computer must be unique, you can’t simply assign an IP address to your computer. Here are 3 recommended IP ranges you can used in your network. These 3 blocks of private IP address space are reserved by Internet Assigned Numbers Authority (IANA) for private network, such as home network. 3 Private IP address space: 10.0.0.0 - 10.255.255.255 172.16.0.0 - 172.31.255.255 192.168.0.0 - 192.168.255.255 You can use these 3 Private IP address space in your network without worrying it will conflict with the IP addresses in Internet. After deciding the IP addresses to be used, let’s decide what netmask to be used. Netmask will decide how many IP addresses available to be used in your network. I usually use 255.255.255.0 for having 254 addresses to be assigned. There is a network address and broadcast address which can’t be used for IP assigning. Network address is used to represent that particular created network, whereas broadcast address is used to talk to all computers in that particular network. Below are some examples for assigning IP addresses in your network. 11 Example 1: I have 5 computers and a router in my network. I will assign 10.0.0.1 to the router, 10.0.0.2 – 10.0.0.6 to other 5 computers. I use netmask 255.255.255.0 for this network, so that I can assign IP addresses 10.0.0.1 - 10.0.0.254 in the network. Network address is 10.0.0.0, broadcast address is 10.0.0.255. Example 2: I have 8 computers, 2 notebooks and a router in my network. I will assign 172.16.10.1 to the router, 172.16.10.2 – 172.16.10.9 to other 8 computers and 172.16.10.10 – 172.16.10.11 to other 2 notebooks. I use netmask 255.255.255.0 for this network, so that I can assign IP addresses 172.16.10.1 – 172.16.10.254 in the network. Network address is 172.16.10.0, broadcast address is 172.16.10.255. Example 3: I have 8 computers, a router and a network printer in my network. I will assign 192.168.1.1 to the router, 192.168.1.2 to the network printer and 192.168.1.3 – 192.168.1.10 to other 8 computers. I use netmask 255.255.255.0 for this network, so that I can assign IP addresses 192.168. 1.1 – 192.168.1.254 in the network. Network address is 192.168.1.0, broadcast address is 192.168.1.255. Try this online simple IP calculator. http://www.subnetmask.info/ Try to enter network address 192.168.1.0 and number of subnet 1, then click calculate. You will get detailed information about this network. Try it.. If you wish to learn more about IP or network subnet, here is useful IP and subnetting site with video presentation. http://www.learntosubnet.com/ For the setup that I’m using, I will use IP addresses 192.168.1.1-254, netmask 255.255.255.0. Install the NIC in its proper place. If it is a PCI card (which it probably will be), make sure it is in snug. 12 Make sure that you place the switch/router in a central location such that each of your nodes has easy access to the switch/router. If the RJ-45 plug is connected on both ends, the light on the switch/router should light up under which port you are using. Do NOT place anything in the uplink port. Power up the switch/router and get ready to rumble. A Note About Windows XP Now that all of your computers are plugged into the network and everything is powered and fine and dandy, you should probably start thinking about the software configuration of your LAN. Assumed in this tutorial is that you have Windows XP. Now, it is obvious that not every single PC user today uses Windows XP. However, the majority of users do, and for the purposes of this guide, I believe that instructions for XP will suffice because many of the instructions used in this configuration tutorial are extremely similar on both Windows 9x and NT/2000 operating systems. Router Configuration 13 Now, load up your Windows XP installation. If everything is physically set up correctly, Windows should “automatically” detect and configure your network connection. That’s it, right? Of course not. Actually, more important than client configuration on any network is the much- feared router configuration process. The router configuration process utilizes the HTTP or Hyper Text Transfer Protocol as an interface to the router’s internetworking operating system. Basically, what that means is that you will interface and configure the router through a web browser. However, here is the fundamental paradox: how is it possible to interface with a router using HTTP when your network is not properly configured in the first place? Hopefully, Windows XP has correctly detected your network settings. Go to Start -> Run and then type in “cmd” to get the almighty command prompt. From the command prompt, type in “ipconfig /all.” If your default gateway is not 0.0.0.0, then type in that IP into your web browser preceded by the “http://” string. Most likely it will be 192.168.0.0, 192.168.0.1, 192.168.1.0, 192.168.1.1, or 192.168.254.254. Whatever the case, once it loads, it will most likely load an authentication applet. Refer to your router’s documentation for this default password. Once your credentials have been accepted by the router, you are ready for action. Now, herein lies a complicated dilemma for this guide. On one hand, it would be easiest for the reader of this guide to read each individual router’s particular method of configuration and such. However, on the other, to cover each and every router would take years. So, refer to router’s documentation when you doubt a reference or in lack of knowledge of the meaning or location of a particular setting. DHCP One of the fundamental concepts of the LAN is the concept of IP addresses. Now arises the question: how exactly are they assigned? The answer is through DHCP. DHCP stands for Dynamic Host Configuration Protocol and basically is used to assign nodes on the network IP addresses automatically such that none conflict with each other (i.e. two nodes sharing the same IP), are legal (i.e. not 192.177.454.4), and are sometimes even in order (192.168.1.10- 192.168.1.20). DHCP works on a client-server level, in that the client (a node on the network) requests a “lease” on an IP from a server (usually the router). The server grants the node a specific IP. Now, you may or may not want to employ DHCP in your LAN setup. There are numerous advantages to DHCP, the foremost being that there is a much lessened chance of two nodes identifying with the same IP address. It is also self/automatically configuring and a very 14 reliable server. In the case that you choose to use DHCP, configure DHCP for which IP addresses you wish it to give leases to start upon and end upon. DMZ and Port Forwarding Now, after DHCP is configured, every member of your network can now be assigned a unique IP address internally. However, externally, the Internet still may need to contact a specific computer in your network for a specific purpose. These purposes include things from Counter-Strike and UT2004 to web servers and MySQL databases. So, how does a computer on the Internet know how to specifically contact a computer in your network (which, through a router, a million computers could potentially be hidden under one IP address)? The port system of TCP/IP provides this option. TCP/IP works on a system of IP addresses and port numbers. Port numbers are specific “holes” or entries to a node on a network for a specific purpose. Ports are infamous for their reputation as “security holes” because it is often through useless open ports that worms spread so powerfully, dangerously, and easily. Now, for example, let’s say you needed to host a file server through FTP. After setting up the file server on your desired node, you will need to find the IP address of that specific node. Then, go to the port forwarding section in your router’s configuration setup dialogue and fill in the port forwarding form accordingly. Remember that FTP operates on Port 21. There is, however, another option. Suppose on your network there is one computer or server that is so important that you feel you cannot individually specify which ports to forward to this computer on, you can set it as the almighty DMZ host. The DMZ host takes all of the non-forwarded ports and sends them straight to the DMZ Host instead of the router itself. The DMZ host role can be fulfilled by anyone, but 15 generally speaking, being the DMZ Host is an invitation to be paid a visit from Bubba the Hacker. It is a wide-open computer system. Just for your information, another term for the “Port Forwarding” section of your configuration software is “Services Configuration.” Now that you have finished with the configuration of your router, you can move on to the configuration of your client. Pray for the Best Windows XP almost always can automatically determine and detect a network connection. To see if it has detected your connection, go to Start -> Control Panel -> Network Connections. Look for the “LAN or High Speed Internet” heading and find your LAN connection under the listing. Note that VPN and 1394 Connections are usually not valid LAN connections and are not what you are looking for. Supposing Windows does not automatically detect your LAN connection for you, recheck your media (cabling) and unplug then replug the RJ-45 into your computer. This is a rare occurrence and usually at the fault of lower-level hardware (or human error). 16 Making Sure TCP/IP Works Next, you will need to double-click your connection. Another dialogue box should come up shortly. To assure you have properly set up this connection, the dialogue box should read “Connected” and have both many sent and received packets. Now, double-click “Properties.” Once the properties dialogue box shows up, click on the text of “TCP/IP” and press “Properties.” Now, make sure you have set it to “Obtain IP Address Automatically” and to “Obtain DNS Automatically.” Recall back to DHCP Configuration. The DHCP Server on your switch/router will assign your computer an IP rather than your computer declare one for itself in order to reduce the stress on the network and to avoid IP collision, or two or more computers claiming the same IP address. Also, remember that the IP addresses assigned by your router are internal ones and are not known to the outside Internet. 17 Once you have completed all of this, “OK” your way out of the dialogue boxes and now go to Start -> Run and type in the Run field “cmd” in order to open up a command prompt. Once the command prompt has opened, type in “ipconfig /all” If your settings show up right away, you are good to go! You have successfully set up a basic TCP/IP network on Windows XP. Now, you are ready to configure your computer for more, but for now, your computer is a new node on a brand new network. 18 Bonus Connect 2 Computers Directly Using Crossover Cable How do you connect 2 computers sometimes for file or printer sharing? Ha! It's pretty easy! You only need 1 crossover cable and 2 network cards . Plug in network card each to computer and then install network card driver for each computer. Connect the cable to both computers’ network card. Yap.. we have finished the setup. Here comes the network configuration, let’s create a simple network by assigning following network info to each computer's network card: Computer A: IP Address: 10.1.1.1 Subnet mask: 255.255.255.0 Gateway: DNS Servers: Computer B: IP Address: 10.1.1.2 Subnet mask: 255.255.255.0 Gateway: DNS Servers: Since these 2 computers are directly connected, no gateway and DNS servers are needed. 19 Here is step-by-step instructions to assign IP address and other network information in Windows 7 Quick Way to Configure IP Address and Other Network Information in Windows 7 Let me show you how to configure IP address and other network information in Windows 7 here. As you know IP address must be configured on computer in order to communicate with other computers, because this IP address is the standard address understood by computers and other networking devices in networking world. You can configure IP address, subnet mask, gateway and DNS servers manually on computer, but you can also configure computer to obtain IP address and other network information from DHCP server (most of the time is configured on router). Without wasting any more time, let me show you quick way to do it: 1) Go to Start and click on Control Panel. 2) Proceed to click View network status and tasks in Control Panel window. 3) Network and Sharing Center window will appear, then click change adapter settings. 20 4) Network Connections window will appears. Here you can right click on the network adapter (can be wireless adapter or wired Ethernet adapter) that you wish to configure and click Properties. 5) In the Network Connection Properties window, tick on Internet Protocol Version 4 (TCP/IPv4) and click Properties. 21 Note: If your computer sits in IPv6 network, you can select Internet Protocol Version 6 (TCP/IPv6) to configure IPv6 address, but it’s not covered here. Manual IP Assigning If you want to do manual configuration, you can now key in the IP address, Subnet mask, Default gateway and DNS servers. Note: IP address of your computer must be unique. None of the 2 computers in the same network can share same IP address, because it will cause IP address conflict. Note: Default gateway is a router that can route the traffic to the other network or Internet. DNS server is an application server that can translate URL to IP address. Check with your ISP on what 22 DNS servers you should use. If not, you can try this free Opendns or Google DNS servers. 23 IP Assigned by DHCP server If you have DHCP server setup on your router or you have dedicated DHCP server, your computer can be assigned IP address and other network information automatically by selecting Obtain an IP address automatically and Obtain DNS server address automatically. Note: If you have a notebook, and you use static IP at home and the IP assigned by DHCP server at the office, you can make use of alternate configuration to set IP and network information for these 2 different networks. Set Obtain an IP address and DNS automatically on General tab as according to what I specified above, so that the notebook will be assigned IP addresses automatically at the office. After that, click Alternate Configuration tab, select User configured option and key in your home network’s static IP and other network information. By setting this, when there is no IP information assigned due to no DHCP server at home, this alternate configuration will be applied automatically, so 24 that you don’t have to spend time on configuring IP manually every time at home. Windows Vista Configuring IP Address and Other Network Information in Windows Vista In this simple article I will show you on configuring IP address and other network information in Windows Vista. The method is almost the same as Windows XP, but the path to access the setting page is different. Here is detailed instruction on configuring IP address and other network information in Window Vista: 1) Go to Start and right click on Network and then click Properties. 2) Network and Sharing Center window will appear, then click Manage network connections. 25 3) Network Connections window will appears. Here you can right click on the network card that you wish to configure and click Properties. 4) In the Local Area Connection Properties window, tick on Internet Protocol Version 4 (TCP/IPv4) and click Properties. Note: If your computer sits in IPv6 network, you can select Internet Protocol Version 6 (TCP/IPv6) to configure IPv6 address. Here I only show IPv4 configuration. 26 Manual IP Assignment You can now key in the IP address, Subnet mask, Default gateway and DNS servers. Note: IP address of your computer must be unique. None of the 2 computers in the network can share same IP address, it causes IP address conflict. Note: Default gateway is a router that can route the traffic to the other network or internet. DNS server is an application server that can translate URL to IP address. As an example, www.cert.org is URL and it can be translated to 192.88.209.6 by DNS server. Check with your ISP on what DNS servers you should use. 27 IP Assigned by DHCP server If you have DHCP server setup on your router or you have DHCP server, your computer can be assigned IP address automatically by selecting Obtain an IP address automatically and Obtain DNS server address automatically. Note: If you have a notebook, using static IP at home and the IP assigned by DHCP server at the office, you can make use of alternate configuration to set IP and network information for these 2 different networks. 28 Set Obtain an IP address automatically on General tab which is same as what I specified above, so that the notebook will be assigned IP addresses automatically at the office. After that, click Alternate Configuration tab, select User configured option and key in your home network’s static IP information. By setting this, when there is no IP information assigned due to no DHCP server at home, this alternate configuration will be applied automatically, so that you don’t have to spend time on configuring IP manually every time at home. Windows XP How to Set IP Address and Other Network Information in Windows XP IP (Internet Protocol) address is the 4 octets (32-bit) address used to identify your desktop computer, notebook, router, switch or other network devices in your network or Internet. It’s also called as IPv4 (Internet Protocol Version 4). IP address is assigned to network card on your desktop computer or notebook to communicate with other network devices. Each IP Octet can be the value between 0 and 255, but several rules exist for ensuring IP addresses are valid. Examples are 192.168.8.145, 10.11.3.4, etc. 29 Here are step-by-step instructions showing you how to set IP address and other network information: 1) Go to Start and click on Control Panel. 2) Control Panel window will appear. Double click on Network Connections. 3) Network Connections window will appear. Right click correct Local Area Connection by identifying correct network card and click Properties. 4) Select Internet Protocol (TCP/IP). Click on Properties. Manual IP Assigning You can now key in the IP address, Subnet mask, Default gateway and DNS servers. Here is IP logical network Designing Guide. Note: IP address of your computer must be unique. None of the 2 computers in the network can share same IP address, it causes IP address conflict. Note: Default gateway is a router that can route the traffic to the other network or Internet. DNS server is an application server that can translate URL to IP address. As an example, www.cert.org is URL and it can be translated to 192.88.209.6 by DNS server. Check with your ISP on what DNS servers you should use. If not, you can try this free Opendns. 30 IP Assigned by DHCP server If you have DHCP server setup on your router or you have DHCP server in home network, your computer can be assigned IP address automatically by selecting Obtain an IP address automatically and Obtain DNS server address automatically. 31 Note: If you have a notebook, using static IP at home and the IP assigned by DHCP server at the office, you can make use of alternate configuration to set IP and network information for these 2 different network. Set Obtain an IP address automatically on General tab which is same as what I specified above, so that the notebook will be assigned IP addresses automatically at the office. After that, click Alternate Configuration tab, select User configured option and key in your home network’s static IP information. By setting this, when there is no IP information assigned due to no DHCP server at home, this alternate configuration will be applied automatically, so that you don’t have to set IP manually every time at home. 32 After assigning IP address, try to ping the other computer from command prompt, 33 How to differentiate straight and crossover cable What are Straight and Crossover cable Common Ethernet network cable are straight and crossover cable. This Ethernet network cable is made of 4 pair high performance cable that consists twisted pair conductors that used for data transmission. Both end of cable is called RJ45 connector. The cable can be categorized as Cat 5, Cat 5e, Cat 6 UTP cable. Cat 5 UTP cable can support 10/100 Mbps Ethernet network, whereas Cat 5e and Cat 6 UTP cable can support Ethernet network running at 10/100/1000 Mbps. You might heard about Cat 3 UTP cable, it's not popular anymore since it can only support 10 Mbps Ethernet network. Straight and crossover cable can be Cat3, Cat 5, Cat 5e or Cat 6 UTP cable, the only difference is each type will have different wire arrangement in the cable for serving different purposes. Straight Cable You usually use straight cable to connect different type of devices. This type of cable will be used most of the time and can be used to: 1) Connect a computer to a switch/hub's normal port. 2) Connect a computer to a cable/DSL modem's LAN port. 3) Connect a router's WAN port to a cable/DSL modem's LAN port. 4) Connect a router's LAN port to a switch/hub's uplink port. (normally used for expanding network) 5) Connect 2 switches/hubs with one of the switch/hub using an uplink port and the other one using normal port. 34 If you need to check how straight cable looks like, it's easy. Both side (side A and side B) of cable have wire arrangement with same color. Check out different types of straight cable that are available in the market here. Crossover Cable Sometimes you will use crossover cable, it's usually used to connect same type of devices. A crossover cable can be used to: 1) Connect 2 computers directly. 2) Connect a router's LAN port to a switch/hub's normal port. (normally used for expanding network) 3) Connect 2 switches/hubs by using normal port in both switches/hubs. 35 36 In you need to check how crossover cable looks like, both side (side A and side B) of cable have wire arrangement with following different color . Have a look on these crossover cables if you plan to buy one. Lastly, if you still not sure which type of cable to be used sometimes, try both cables and see which works. Note: If there is auto MDI/MDI-X feature support on the switch, hub, network card or other network devices, you don't have to use crossover cable in the situation which I mentioned above. This is because crossover function would be enabled automatically when it's needed. if you need complete ebooks visit