UNDERSTANDING INTERNET ADDRESSES IP ADDRESS

UNDERSTANDING INTERNET ADDRESSES

IP ADDRESS

An IP address (Internet Protocol address) is a unique address that certain electronic devices use in order to identify and communicate with each other on a computer network utilizing the Internet Protocol standard (IP)—in simpler terms, a computer address. Any participating network device—including routers, switches, computers, time-servers, printers, Internet fax machines, and some telephones—can have theirown unique address. In other words, the IP address acts as a locator for one IP device to find another and interact with it. It is not intended, however, to act as an identifier that always uniquely identifies a particular device.

SUBNET MASK (SUBNETWORK MASK)

The technique used by the IP protocol to create a subnet address. The subnet mask is a binary pattern that is stored in the client machine, server or router. It is matched with the IP address of a packet to determine which network segment the packet is destined for.

A Tradeoff between Hosts and Subnets

Depending on the network class (A, B or C), some number of bits are reserved for hosts and subnets, and these bits become a tradeoff. The more hosts, the fewer the subnets can be created; the more subnets, the fewer the hosts can be individually addressed.

A Subnet Mask Example

The subnet mask below is a Class C address, which uses the first 24 bits for network ID and the last 8 for host ID. These last 8 can be divided between hosts and subnets. In the default mask below, the 0

means there are no subnets and up to 254 hosts can be addressed.

In the second example, the 224 reserves the three high-order bits of that field for subnets, leaving the remaining 5 bits for hosts. This 224 pattern creates subnets in the range of 001 to 110 (000 and 111 are reserved). As such, 6 subnets of up to 30 hosts in the range of 00001 to 11110 can be addressed. Once

again, 00000 and 11111 are reserved: all zeros mean "this" node, and all ones mean "all" nodes (broadcast), which is why calculations for maximum hosts and subnets are always subtracted by 2. For a list of all Class B and C subnet masks.

Class C Default Submask

255.255.255.0

11111111.11111111.11111111.00000000

Class C Subnet Mask (6 Subnets/30 Hosts Each)

255.255.255.224

11111111.11111111.11111111.11100000

Following is a list of all Class B and C subnet masks and their maximum hosts and subnets. The last two octets (16 bits) of Class B and the last octet (8 bits) of Class C addresses are divided between hosts and subnets. At the end, all Class C masks are shown in more detail.

CLASS B SUBNET MASKS

Subnet Mask How 16 Bits Are Divided Maximum Subnets Maximum Hosts

255.255.192.0 2/14 2 16,382

255.255.224.0 3/13 6 8,190

255.255.240.0 4/12 14 4,094

255.255.248.0 5/11 30 2,046

255.255.252.0 6/10 62 1,022

255.255.254.0 7/9 126 510

255.255.255.0 8/8 254 254

255.255.255.128 9/7 510 126

255.255.255.192 10/6 1,022 62

255.255.255.224 11/5 2,046 30

255.255.255.240 12/4 4,094 14

255.255.255.248 13/3 8,190 6

255.255.255.252 14/2 16,382 2

CLASS C SUBNET MASKS

Subnet Mask How 16 Bits Are Divided Maximum Subnets Maximum Hosts

255.255.255.192 2/6 2 62

255.255.224.224 3/5 6 30

255.255.240.240 4/4 14 14

255.255.248.248 5/3 30 6

255.255.252.252 6/2 62 2

Domain Names

The unique name that identifies an Internet site. Each domain name has two parts (or more) separated by a dot: the part to the left of the dot is specific, and the part to the right of the dot is more general indicating the logical venue of a site according to the following: edu for education, gov for government agency, net for network related, com for commercial, org for organization (nonprofit or research oriented). Outside the United States, the part to the right of the dot may also indicate the geographical venue of a site, such as ca for Canada, uk for United Kingdom, jp for Japan, fr for France. Domain names must be registered, and some users will register many domain names, even though they

have no intention of using them, simply to later sell at a profit or to prevent any competitor from using

them.

Work Group

Work group is the unique name assigned to the group of computers for deciding their logical boundry. When computers are part of workgroup they are in peer to peer architecture.

Broadcast Address

In computer networking, a broadcast address is an IP address that allows information to be sent to all machines on a given subnet rather than a specific machine. The exact notation can vary by operating system, but the standard is laid out in RFC 919.

Example: to broadcast a packet to an entire class B subnet using a private IP address space, the

broadcast address would be 172.16.255.255.

This can be found from the subnet mask (255.255.0.0) and the IP address (eg. 172.16.48.196) - the

complement of the subnet mask is 0.0.255.255, and 172.16.48.196 | 0.0.255.255 = 172.16.255.255.

A special type of IP address is the limited broadcast address 255.255.255.255. A broadcast involves delivering a message from one sender to many recipients. This broadcast is 'limited' in that it does not reach every node on the Internet, only nodes on the LAN.

Other Protocols

IPX

The Novell IPX protocol allows broadcast as well. When the network address is specified as FFFFFFFF, the packet is to be sent to all the networks available. When the target node address is specified as FFFFFFFFFFFF, the packet is intended to be received by all the computers in the network.

Ethernet layer

Broadcast is possible also on the underlying data link layer. Ethernet frames can be addressed to every computer on a given LAN segment if they are addressed to MAC address FF:FF:FF:FF:FF:FF. Ethernet frames that contain IP broadcast packages are usually sent to this address. ARP typically uses segment-

wide broadcast for its queries.

Default gateway

A default gateway is a node (a router) on a computer network that serves as an access point to another network.

In homes, the gateway is usually the ISP-provided device that connects the user to the Internet.

In enterprises, however, the gateway is the computer that routes the traffic from a workstation to the outside network. In such a situation, the gateway node often acts as a proxy server and a firewall. The gateway is also associated with both a router, which uses headers and forwarding tables to determine where packets are sent, and a switch, which provides the actual path for the packet in and out of the gateway.

In other words, it is an entry point and an exit point in a network

Usage

A default gateway is used by a host when an IP packet's destination address belongs to someplace outside the local subnet (thus requiring more than one hop of Ethernet communication). The default gateway address is usually an interface belonging to the LAN's border router.

Preferred DNS Servers

All communications on the internet is by a number (IP address to IP address) Preferred DNS server

handles this for you so you can use names without having to use numbers.

The Gateway is simply an address / portal which goes to some other network. If you are on your local network the gateway takes you to the internet or to a different local network. (It is the path to outside your local system.) If you have a local router its local address is your gateway address. If you don't have a router or from inside your router, your ISP has a "gateway" addresses to get you outside of their local system.

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