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Showing posts from 2006

Ethernet Hub - Physical Layer Device

Hub is a network device connects multiple devices and makes single network segment. Hub works in Physical layer of OSI Reference Model. Since it is a layer one device, it does not have the feature to read the signals it transmits. All the devices connected to the hub feel they are connected to the same physical wire. So we can say hub has single collision domain. In other words, a hub simply repeats the signal it receives. Let us check the working of hubs. How Hubs work When a computer connected to a hub sends packets, hub broadcast the packets to all the ports except the one it came from. Here we can see the difference between Switch and hub. Hub does not read the packets and it broadcast to all ports but Switch is intelligent device and read the packet and just unicast it. So Switch is more efficient compared to a hub. Another problem with the hub is the higher the chances of packet collisions. We know hub has single collision domain and the chances of a collision are very hi

Internet Control Message Protocol (ICMP)

One of the important parts we need to do while troubleshooting a network is to check the connectivity of two devices. We have many utilities to check the connectivity and availability of destination device. All these utilities are based on ICMP, defined in RFC 792. Internet Control Message Protocol (ICMP) is used to send error and control information between devices which support TCP/IP. Utilities like ping, tracert, pathping, etc work using ICMP. This tutorial explains the functions of Internet Control Message Protocol and the list of error messages generated by ICMP. Important Functions of ICMP Send echo requests from a TCP/IP device to another Responds to Echo request Helps to find routing path issues ICMP echo message verify the availability of the destination List of Messages Generated by ICMP Address Request Address reply Destination unreachable To learn more about the Destination unreachable message generated by Internet Control Message Protocol, vis

DMZ In Network Security (Demilitarized Zone)

Now, most of the modern Small Office Home Office routers offer DMZ host feature. For those who don't know about the use of DMZ, this tutorial may give an overall idea about it. If you place a device in your network in DMZ, that device won't have much access to other devices connected to the network. A device placed in DMZ is more exposed to external threats as it is logically placed outside the network with limited security. Also, all ports of DMZ host are open and exposed to the external network. DMZ host has its own merits and demerits. What is The Use of DMZ in a Network If you are a hardcore online gamer, you know the hurdles created by the router firewall and NAT. In most cases simple port forwarding allows you to continue online gaming but rarely some users face issues. The ultimate solution for the firewall issues in online gaming is to place your gaming computer in DMZ. However, after this step, your gaming computer is no longer protected by router firewall. Als

Network Address Translation( NAT)

Network Address Translation (NAT) allows you to convert one IP address into another address. Address Translation process changes the IP address information in a packet to a different address. NAT feature is introduced to solve two major issues faced in networking: face the shortage of IP addresses and hide the network scheme. Now the major function of Address Translation is to convert the private IP addresses in a network into a public IP address. This tutorial explains the major functions, different types and working of NAT. Different Types of Address Translation Address Translation is of different types depends on the way and the number of IP addresses they translate. Static NAT In Static Network Address Translation, one IP address in a packet is translated to different IP address manually. It is one to one mapping. Dynamic NAT In Dynamic Network Address Translation, address translation device picks an IP address dynamically to convert from a list of allowed IP addresse

Dynamic Host Configuration Protocol (DHCP) CCNA Exam Tutorial

The Dynamic Host Configuration Protocol (DHCP) allows devices to dynamically get IP address information. It is very important in networks especially for big networks because it assigns IP addresses to each device in the network automatically. Think about a network having thousands of devices. It is very difficult to assign static IP addresses to each device without having errors. Here Dynamic Host Configuration Protocol helps us. This protocol assigns an IP address to each device without any errors and is very easy to manage. It contains two parts, the server, and client. Working of Dynamic Host Configuration Protocol We can simply use the term DORA to explain the working of DHCP. It is a four-stage process and each stage is explained below. D-- DHCP Discovery When a client connected to a network, it sends a broadcast to discover the DHCP server. This broadcast is termed as DHCPDISCOVER. O--- DHCP Offer At this stage, the server responds to the client DISCOVERY message

Fundamentals of Ethernet

Ethernet is LAN media type that uses CSMA/CD to send information and functions at Data Link Layer of OSI Reference Model. Ethernet media type having different physical topologies but having single logical topology: bus topology. With various physical topologies, we can design this network with different shapes but the communication happens in Bus topology only. It has two versions right now. One of them is DIX version and the second is IEEE version. This tutorial explains various topologies and versions of Ethernet. Physical Topologies Supported Bus topology Star Topology Point to Point Uses of Netstat Command Transport Layer in a Network PING: Transmit failed. General Failure Destination Net Unreachable Destination host unreachable Enable Disabled Adapter Resolve Windows Automatic IP Hard Disk SMART Command Failed Error Solve TTL Expired in Transit Ping Request Could not Find Host Two Versions Of Etherne

What is WiFi & Different IEEE 802.11 Wireless Standards

Wi-Fi is the term used to denote Wireless Local Area Networks which are using IEEE802.11 wireless standards. Now the term WiFi is representing all Wireless Local Area Networks. Wireless technologies used in WiFi are IEEE 802.11a, b, g, n, and ac. In this tutorial let us check what is WiFi and the major 802.11 standards. You can also see a list of WiFi devices which supports them. At the end of the tutorial, you can see a backward compatibility checker chart. Using this chart you can take decisions related to extending your WLAN networks. With the help of the chart, you can avoid situations of buying a device which is not compatible with existing devices (standards which are not backward compatible). IEEE 802.11 Wireless Standards Available In Industry IEEE802.11a IEEE802.11b IEEE802.11g IEEE802.11n IEEE802.11ac Solve TTL Expired in Transit Functions of Transport Layer PING: Transmit failed. General Failure Destination Net Unreachable D

IP Addressing Guide (IPv4 & IPv6 Addressing)

The IP address is the third layer address in TCP/IP Protocol Stack, given to each device connected to a network. In Internet layer of TCP/IP Protocol Stack, each device in a network is assigned with a unique address known as IP address. There are two versions of TCP/IP: IPv4 and IPv6. Right now we are using IPv4 version to assign a logical address to devices in a network. In this tutorial, you will learn the differences between IPv4 addressing and IPv6 addressing with different classes of IPv4 addresses. Differences Between IPv4 and IPv6 Length IPv4 is 32-bit address broken into four octets which are separated by a period. IPversion6 is 128-bit long address having the capability to give more addresses than IPversion4 offers. Examples of IPversion4 and IPversion6 addresses are given below. IPversion4 addressing : or in binary form 00001010 00000000 00000000 00000001 IPv6 addressing : E3D7:0000:0000:0000:51F4:9BC8:C0A8:6420 Representation IPv6 is a 128-bit binary

Bluetooth Technology

Bluetooth is a short distance wireless technology defined as IEEE 802.15.1 to create Personal Area Networks. Right now Bluetooth is widely used in mobile phones to send and receive data. According to Bluetooth technology, there are a master and slave devices. A master device can connect to a maximum of seven slaves at a time. The frequency of Bluetooth is similar to IEEE 802.11 g/b. It is in the range of 2.4 to 2.485 GHz. Major advantages of Bluetooth over Wi-Fi is its low cost and low power. However, Wi-Fi has a wider range and faster data transfer rate. Major Uses of Bluetooth Technology There are a variety of applications run with the help of Bluetooth technology. Some of the uses are: Make an easy connection between mobile phones to send and receive files Bluetooth technology enables wireless mouse and keyboard Create a Local connection between PCs Helps to create a short-range wireless network Reset a Router Manually How To Power Cycle a Modem Setup Lin

Basic Wireless Networks Tutorial

A wireless network uses the wireless signal to communicate between devices connected in the network. Here we use signals like radio waves, microwaves or infrared to send and receive data between two devices. Just like normal network types, they too classified into Wireless LAN, MAN, WAN etc. They are mentioned as WLAN, WMAN, and W-WAN respectively. This article gives you a brief introduction to each type of WiFi networks. We order them below according to the size of the area they cover. < Uses of Netstat Command Functions of Transport Layer PING: Transmit failed. General Failure Destination Net Unreachable Destination host unreachable Enable Disabled Adapter Windows Automatic IP Address Hard Disk SMART Command Failed Solve TTL Expired in Transit Ping Request Couldn't Find Host Types of Wireless Networks WPAN Wireless Personal Area Network (WPAN) uses to transfer data between two devices which are in short distan

What is Router & Major Functions

A router is a layer three (Network Layer in OSI Reference Model) device used to connect different networks. For example, if you want to connect two networks one is FDDI and other is Ethernet, we need a router. It also connects networks with the different network address. To move information between devices having different network numbers, we need a layer 3 device. Routers can switch packets on the same interface using VLANs. Router and Routing Tables The router makes routing decisions based on the routing table it has. Routing table consists of path information to send packets to neighboring routers. Routing table with routing protocols helps router to find the shortest path to send packets to the destination. Examples of Routing Protocols Interior Gateway Routing Protocol (IGRP) Routing Information Protocol (RIP) Address Resolution Protocol (ARP) Internet Control Message Protocol (ICMP) Dynamic Host Configuration Protocol (DHCP) Functions of Router We c

Functions of Wide Area Networks (WAN) Tutorial

Wide Area Networks(WAN) covers a large area extends from countries to continents. It is used to connect LANs together. It is like when we need to connect two LANs at different locations separated by a long distance, we need WAN to connect them. There are different WAN services used to connect different LANs situated at different locations. Cable and DSL are the two most popular WAN connections. Other than these two, there is a list of WAN services available. List of Popular WAN Services Digital Subscriber Line (DSL) Cable Dedicated circuits ATM Analog Dialup Frame Relay ISDN X.25 SMDS (Switched Multi-megabit Data Services) Popular Connection Types Used in WAN Services There are four different connection types used in Wide Area Networks service. They are: Circuit-switched : Circuit-switched services provide a temporary connection using a phone circuit. Analog dialup and ISDN are examples of circuit-switched WAN connection types. Cell Switched

Metropolitan Area Network (MAN)

Metropolitan Area Networks in short MAN usually covers the area of a metropolitan city and is a hybrid between LAN and WAN. This type of networks covers a few kilometers. The cable TV network is an example of Metropolitan Area Network. But there is a difference. MAN is a computer network but cable TV connection provides TV broadcast. In a Metropolitan Area Network, two buildings in a city are connected and start data transfer. That means this connect two devices which are located far away but limited to a metropolitan location. It has the size of a metropolitan city. One of the differences between WAN and MAN is the connection speed. WAN offers low to medium connection speed but Metropolitan Area Network offers high-speed connection. Technologies Used in MAN ATM (Asynchronous Transfer Mode) FDDI SMDS Ethernet-based MAN Functions of Transport Layer PING: Transmit failed. General Failure Destination Net Unreachable Destination host unreachable Ena

Basics of Computer Networking

A network consists of all devices connecting each other in order to communicate between them across a small or large distance. Major components in it are computers, connecting cables, router, switch etc. It is important to create a network to improve the efficiency of users by allowing them to send and receive information easily. They are classified into LAN, MAN, and WAN according to the area it covers. Let us check each type of networks here. Network Types LAN To read more about LAN, click the link below. Local Area Network MAN For the details about the Metropolitan Area Network, click the link below. Metropolitan Area Networks WAN To learn more about it, click the link below. Wide Area Network Wireless Networks To learn more about it, visit the link below. Wireless Networks Major Components in a Computer Network All the hardware and software parts included in a network are network components. It includes computers, storage devices, hubs and switches,

Local Area Network (LAN) -CCNA Study Material

Local Area Network(LAN) is used to connect networking devices in a small area like an office or campus building. The media type used to connect devices in a Local Area Network(LAN) is Ethernet, FDDI, Token Ring etc.  LAN helps to communicate between devices in a smaller area and improve the efficiency of working in an office. Let us consider common topologies used in Local Area Network because it is in CCNA Exam Syllabus.  It is classified into the physical and logical topology. In Physical Topology, you can see how devices in a LAN are connected but in Logical Topology, we can see how these devices are communicating. LAN Physical Topologies Point to Point Here two devices are connected without any interference from other devices. In this LAN topology, these two devices are connected and communicated. Wireless Bridge is a good example of Wireless Point to Point Topology. How to Configure Linksys WAP54G into Wireless Bridge Mode Bus T You can say it is an extension of Point

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Alex George
Alex George has Engineering graduation in Computer Science and an MBA in Finance. He had been working as a senior Network Engineer for ten years. His specialization is in Cisco products. Traveling is one of his hobbies and visited various places as part of his onsite work. He visited different places as part of his onsite work like New York, Dubai, London, etc. Right now Alex is a director of one of the leading career development firms in India, which trains students for UPSC, SSC, and PSC examinations. He guides a lot of students to get selection for various prestigious institutions like CBI, Income Tax Department, etc. Alex George is a stock market investor and a very active intraday trader. Engineering Background: He has a B.Tech in Computer Science and Engineering and passed different network and security courses like CCNA, CCNP (Security), CEH, and various Microsoft certifications. Finance Background: Alex has an MBA in Finance. He is an active intraday trader and a Share Market Investor. Webmaster Skills: Alex is a blogger since 2004. He has a working knowledge of HTML, CSS, PHP, and JavaScrip.