Improtant Networking Devices

Computer network devices also known as communication devices and they constitute a data communication network. These devices are routers, switches, hubs, LAN cards, gateway, modems, hardware firewall, CSU/DSU, ISDN terminals and transceivers. In an Ethernet or WAN network, the data communication cannot be performed without these devices. Being an IT professional or a network administrator, you must have the good understanding of these devices.

Based on your business requirements, you have the select the best devices for your network and before selection, make sure that they are compatible with each other. It is recommended that you select all the devices for your IT infrastructure from the same vendor.

The top vendors are Cisco, D-Link, LinkSys, Baynet, RealTek, 3Com, NetGear, Intel, Nortel, and Lucent etc. A well designed IT infrastructure with the proper placement of the routers, servers, gateway and switches can reduce the operational cost and enhances the overall performance dramatically.

Routers :

A router is a communication device that is used to connect two logically and physically different networks, two LANs, two WANs and a LAN with WAN. The main function of the router is to sorting and the distribution of the data packets to their destinations based on their IP addresses. Routers provides the connectivity between the enterprise businesses, ISPs and in the internet infrastructure, router is a main device. Cisco routers are widely used in the world. Every router has routing software, which is known as IOS. Router operates at the network layer of the OSI model. Router does not broadcast the data packets.

Switches

Like the router, a switch is an intelligent device that maps the IP address with the MAC address of the LAN card. Unlike the hubs, a switch does not broadcast the data to all the computers, it sends the data packets only to the destined computer. Switches are used in the LAN, MAN and WAN. In an Ethernet network, computers are directly connected with the switch via twisted pair cables. In a network, switches use the three methods to transmit the data i.e. store and forward, cut through and fragment free.

Hubs

The central connecting device in a computer network is known as a hub. There are two types of a hub i.e. active hub and passive hub. Every computer is directly connected with the hub. When data packets arrives at hub, it broadcast them to all the LAN cards in a network and the destined recipient picks them and all other computers discard the data packets. Hub has five, eight, sixteen and more ports and one port is known as uplink port, which is used to connect with the next hub.

Modems

A modem is a communication device that is used to provide the connectivity with the internet. Modem works in two ways i.e. modulation and demodulation. It coverts the digital data into the analog and analog to digital

LAN Cards

LAN cards or network adapters are the building blocks of a computer network. No computer can communicate without a properly installed and configured LAN card. Every LAN card is provided with a unique IP address, subnet mask, gateway and DNS (if applicable). An UTP/STP cable connects a computer with the hub or switch. Both ends of the cable have the RJ-45 connectors one is inserted into the LAN card and one in the hub/switch. LAN cards are inserted into the expansion slots inside the computer. Different LAN cards support different speed from 10/100 to 10/1000.

Multiplexer

Multiplexer is a device that is used to combining the several electrical signals into one signal.

DHCP information

In this section you will learn the DHCP router overview, dynamic host configuration protocol overview, network tutorials, troubleshooting tips, subnetting, IP addressing. DHCP or Dynamic Host Configuration Protocol is a network protocol, which is configured in such a way that is provides the IP addresses to the network computers automatically. There is no need to assign the IP address to the client computers individually. DHCP assigns the IP addresses from the given range of the numbers also called DHCP scope.

On the other end, client computers are configured in such a way that they get the IP addresses automatically from the DHCP server during the boot up process. Additionally, DNS and WINS servers can also be configured with the DHCP server.

When a computer starts up it gets the IP addresses from the DHCP server from the defined pool of addresses.
The assigning of the IP address by the DHCP server can be categorized as follows

1. A user turns on the computer with the DHCP client enabled on it.
2. The client PC sends broadcast request (known as DHCP DISCOVER) and then look for the DHCP server to answer.
3. The DHCP server receives the DISCOVER packet and based on the availability and defined settings, the server choose any available IP address and then give to the client. Then DHCP server sends back to the client with DHCP OFFER with that available address information.

4. Again client sends a request to DHCP server known as DHCP REQUEST, in which it lets the server know that it is using the address offered by the DHCP.

5. The DHCP server then again send a acknowledgement to the client known as DHCP ACK, in which it confirm the client that the specific IP address has been assigned to it for a given period of time.

This process of assigning the IP addresses by the DHCP server also known as DORA (Discover, Offer, Request, and Acknowledgement).

When a computer uses a static IP address there can be the chances of error and conflict when two computers use the same IP address. By using the DHCP server there are no chances of such kind of conflicts and errors.

Along with the IP addresses, the DHCP server also enables the client computers to extract all the settings and configurations from the DHCP server on an IP network. These settings include the Firewall, Router, DNS, NAT, WINS, Gateway and Subnet masks settings.

The overall purpose of the DHCP server is to reduce the workload and error margins, which can occur in assigning the IP addresses manually.

The IP address assigned by the DHCP server is for the limited or leased period of time and if a client needs an to extend that leased period for the IP address then client must send a extension request to the DHCP server before this period expires. If the client do not send an extension request, then this IP address becomes free on expiration and is assigned to another client. If a user wants to change the IP address given by the DHCP server then he/she do it by giving these commands on the command prompt.

“IPconfig/release then IPconfig/renew”.

This command will remove the current IP address and assign a new IP address to the client.
There can also be some reserved addresses based on the MAC address or hostname of the client. These reserved addresses are fixed addresses and can only be assigned to the fixed clients.

How to Configure a Network

In this section you will learn how to configure a network, peer to peer, client server, workstation, server, basic data communication