How To Connect Two Computers Directly

How to Connect Two Computers Directly By Bipul Kumar Bal

When you don’t have any HUB or Switching device, you may face problem with connecting two computers directly with the CAT5e or Category 5 cable. Now I will mainly focus on the case where you don’t have any hub. Initially I will describe all the things required in short, and then it is been described vividly.

Short Description • Choose a network address for both the computers say 144.16.192.245 and 144.16.192.247 • Connect the two computers with the CAT5e cable. Now here is the main difference with connecting through hub. In case of hub both end of the cable will have the same color code (Later it has been described as Straight Through). But in case of our case (direct connection) we need different color code for two ends. This color code is called Cross-Over, later it has been described. • Configure the computers for networking, see the vivid description for this section. I hope you will be able to connect two computers directly. Best of luck

Vivid Description 1. Choose a Network Address o o

Any network address will do for this purpose, so long as you understand the basics of how IPv4 works as explained below. IPv4 (IP ver. 4) addresses are written like this: xxx.xxx.xxx.xxx (four number groups separated by three dots), in all RFC-1166 compliant countries. Each number ranges from 0 to 255. This is known as "Dotted Decimal Notation" or "Dot

Notation" for short. The address is divided into two portions: the network portion and the host portion. For "Classful" networks, the network and host portions are as follows: ("n" represents the network portion, "x" represents the host portion) When the first number is 0 to 127 - nnn.xxx.xxx.xxx (ex. 10.xxx.xxx.xxx) These are known as "Class A" networks. When the first number is 128 to 191 - nnn.nnn.xxx.xxx (ex. 172.16.xxx.xxx) These are known as "Class B" networks. When the first number is 192 to 223 - nnn.nnn.nnn.xxx (ex. 192.168.1.xxx) These are known as "Class C" networks. When the first number is 224 to 239 - The address is used for multi-casting. When the first number is 240 to 255 - The address is "experimental". Multicast & Experimental addresses are beyond the scope of this article. However, because IPv4 does not treat them the same way as other addresses they should not be used. For simplicity "non-classful networks" and sub-netting will not be discussed, as we will be connecting only two devices. The network portion specifies a network; the host portion specifies an individual device on a network. For any given network: ƒ

The range of all possible host portion numbers gives the Address Range.

(ex. 172.16.xxx.xxx the range is 172.16.0.0 to 172.16.255.255) ƒ The lowest possible address is the Network Address. (ex. 172.16.xxx.xxx the network address is 172.16.0.0) This address is used by devices to specify the network itself, and cannot be assigned to any device. ƒ The highest possible address is the Broadcast Address. (ex. 172.16.xxx.xxx the broadcast address is 172.16.255.255) This address is used when a packet is meant for all devices on a specific network, and cannot be assigned to any device. ƒ The remaining numbers in the range are the Host Range. (ex. 172.16.xxx.xxx the host range is 172.16.0.1 to 172.16.255.254) These are the numbers you can assign to computers, printers, and other devices. Host Addresses are individual addresses within this range. 2. Connect the two computers together. To connect with a Crossover cable, simply plug an end of the cable into the Ethernet Port of each computer. o To connect with a Hub or Switch, use two straight through cables to connect each computer to the switch or hub. o See "Things you will need" section for more information on "Straight Through" -vs- "Cross-Over" Cables. 3. Configure the computers for networking. Go to internet options (this varies depending on the Operating System), and go to the dialog box that lets you change the TCP/IP protocol. Change the radio buttons from "Obtain from DHCP server automatically" to "Use the following IP address:". o

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Give each computer a different address from the host range. Do not use the network address or the broadcast address. Leave the "Default Gateway" and "DNS server" fields blank. For the subnet mask, use the following: Class "A" Networks When the first number is 0 to 127

The Mask is - 255.0.0.0 Class "B" Networks When the first number is 128 to 191 The Mask is - 255.255.0.0 Class "C" Networks When the first number is 192 to 223 The Mask is - 255.255.255.0 IPv4 originally used the first number (ex. 192) to determine which part of the address is network and which part is host based on the address class. However, the advent of subnetting and nonclassful networking made it necessary to provide a mask because other ways of dividing the address into network and host portions are now possible.(More information in the Important Notes section.) 4. Verify connectivity. The simplest way to do this is with Ping. Bring up MS-DOS or the equivalent on other OS's, (In Windows open the command prompt which is located in the Start Menu - Accessories Command Prompt) and type in: "ping [insert IP address of the other computer here] (ex. 192.168.1.1). If you cannot reach the other computers address, read over the steps again or contact a professional.

Tips • •

To share your files, right click on any folder and choose Sharing to make them shared. You can also do this with your printers to be able to print from one computer while the printer is connected to the other.

Things You'll Need •

Straight Through -vs- Cross-Over o

Straight through is a CAT-5, CAT-5e, or CAT-6 Ethernet Cable with the wires connected as follows:

On both ends: Orange Stripe; Orange; Green Stripe; Blue; Blue Stripe; Green; Brown Stripe; Brown. o

Cross-over is a CAT-5, CAT-5e, or CAT-6 Ethernet Cable with the wires connected: On one end: Orange Stripe; Orange; Green Stripe; Blue; Blue Stripe; Green; Brown Stripe; Brown On the other end: Green Stripe; Green; Orange Stripe; Blue; Blue Stripe; Orange; Brown Stripe; Brown The above conforms to TIA/EIA-568 standard, however, all that is important for a cross-over to work is for pins 1 & 2 (transmit) to switch places with pins 3 & 6 (receive) on the opposite end. For a strait through pins should be the same on both ends. Color sets (ex. Orange Strip & Orange) mark twisted pairs. Keeping pin sets on the same twisted pair (i.e. pins 1 & 2 on one color set, and pins 3 & 6 on another) allows best signal quality.

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Note: TIA/EIA standard has not been established for CAT-7 or greater cabling.

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A cross-over cable is all you need to connect two computers directly.

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You may wish, however, to purchase a switch/hub with two Standard "Straight-Through" Ethernet Cables. This is especially useful if you plan to add more computers later. Note: If planning to connect 3 or more computers, hubs are less expensive but waste bandwidth by repeating all signals out all ports leaving it to the receiving computers to ignore packets not addressed to them. Switches allow more efficient use of bandwidth by sending packets only to the intended recipient.

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Many computers can determine if you are using a crossover or straight through cable. If you are not so lucky to have auto-sensing on at least one of the devices connected by a cable, you must use the correct type between them. Computer-to-switch/hub will require a straight through, computer-to-computer a crossover.

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Check to see if your computer has an Ethernet Adapter in the back of the computer. Most new computers have this. You can tell by the documentation from the computer or by looking at the back of the computer. It looks like a phone jack, but larger, with 8-pins. Do not confuse this with a "modem" jack for dial-up phone service. Phone/modem jacks will have 2, 4, or 6 pins.

Important Notes •

The concept of a subnet mask. The general concept will help in understanding what this number does, and why it matters. Dotted decimal notation is a human way of writing IP Addresses to make them easier to work with. What the computer "sees" is 32 ones and zeros in a row like this: 11000000101010000000001000000000. IPv4 originally broke this into 4 groups of 8, hence the "dots" 11000000.10101000.00000010.00000000, each group is an "octet" of 8 bits. Dotted decimal writes the value of the octet in decimal to make it easier for people to read - 192.168.2.0 A complex set of rules concerning the order of the ones and zeros in the first octet was used to create the "Classful Addressing Scheme"; however, no subnet mask was needed. For all Class A's the first octet was network, for Class B's the first and second were network, for Class C's the first three. In 1987, intra-nets started becoming larger and the Internet was on its way. Wasting whole Class C ranges of 254 host addresses on small networks became a problem. Class A and B networks often wasted addresses because physical limitations forced networks to be divided by routers before they could get large enough to use so many addresses. (Class B's host range (256 X 256) - 2 = 65534 addresses; Class C's (256^3) - 2 = 16,777,214.) Subnetting divides a large Classful network into many smaller "subnets" by increasing the number of ones and zeros used to address networks(leaving fewer for the hosts in each network). A small subnet can then be assigned to a small network without using a large number

of extra addresses. To say which bits are the network address we use a 1. The "mask" (ex. 255.255.255.192) when converted to binary (ex. 11111111.11111111.11111111.11000000) defines exactly how many more bits are added to the network portion (ex. two host bit). In this example, one Class C with 254 hosts becomes four sub-nets with 62 hosts each. Of these sub-nets only two may be assigned to networks; the first and last cannot be used according to RFC-950. Further discussion of the rules of subnetting is beyond the scope of this article. What matters here is that even though we are using Classful addresses, Windows (and other software) doesn't know this. And hence, will still need a mask to tell it how many bits we want to use for the network portion. By saying 255.255.255.0, we're saying that 11111111.11111111.11111111.00000000 is the subnet. By that, we say that the first three octets are the network, and the last is the host - we want to make it a Class C.