NETWORKING BASICS
A exchange ideas can be real clear as the interconnection of self-governing computers related collected to facilitate communication while networking is the uncomplicated conception of connected computers.
Networks and networking have full-grown exponentially more than the last 15years; they have evolved on effortless momentum immediately to keep awake with huge increases in rudimentary significant abuser needs such as allocation facts and printers, as satisfactorily as extra superior burden such as record conferencing.
TYPES OF NETWORKS
LOCAL AREA NETWORK (LAN)
A LAN (Local Area Network) is a congregate of computers and network plans joined concurrently, usually inside the similar construction. A Restricted Locale Network (LAN) is a high-speed transmission system considered to link computers and supplementary records processing devices collected surrounded by a minor geographical locale, such as a workgroup, department, otherwise building. Resident Area Networks realize common admittance machinery. This means that all the devices attached to the LAN share a unattached means of communication medium, mostly a coaxial, twisted match up otherwise fibre optic cable.
METROPOLITAN Quarter NETWORK (MAN)
Metropolitan region networks before MANs are heavy laptop networks mostly on both sides of a urban otherwise a civic. They typically get through wireless infrastructure or optical fibre connections to link their sites.
The IEEE 802-2001 standard describes a MAN as being: "A MAN is optimized for a larger geographical region than is a LAN, ranging as of some blocks of buildings to full cities. MANs can also depend resting on communications channels of moderate to lofty facts rates. A MAN strength live owned and operated by a single organization, nevertheless it frequently will live second-hand by many folks and organizations. MANs might too be present owned and operated as shared utilities. They will frequently endow with way for internetworking of restricted networks. Metropolitan region networks can span positive to 50km."
WIDE Quarter NETWORK (WAN)
Wide Quarter Network (WAN) is a computer network that covers a broad quarter. A Weak in compares to a MAN, is not confidential to a geographical location, even if it might live controlled to a geographical locations, it might too ensue confined inside the bounds of a testify or else country. A Ineffectual connects some LANs, and may live some degree of to an enterprise (a corporation otherwise organization) before accessible to the public.
The technology is prohibitive rapidity and fairly costly. The INTERNET is an example of a worldwide shared WAN.
NETWORKING DEVICES
ROUTERS
Routers are used to connect networks collected and forward packets of data from one network to another. Routers, by default break positive a broadcast realm, which is the obstinate of all devices on a network segment that hear all broadcasts sent resting on that segment.
Routers in addition fall foul of awake collision domains. This is an Ethernet term used to describe a network scenario where one special contraption sends a packet on a network segment, forcing every new device by that segment to pay attention to it. At the matching period, a discrete logo tries to transmit, top to a collision, following which together devices essential retransmit one on a time.
Routers hurry on the layer 3 of the OSI (Open System Interconnection) reference model.
SWITCHES
Switches are worn representing network segmentation based resting on the MAC addresses. Switches look by the incoming build's hardware addresses before deciding to moreover to the fore the frame before drop it.
Switches break down in the lead crash domains but the hosts on the alter are stagnant members of one cumbersome televise domain.
HUB
A nucleus is really a various harbor repeater. A repeater receives a digital gesture and re-amplifies or regenerates that gesticulate, and then forwards the digital gesture out each and every one lively ports without looking on some records. An active center does the similar entity. This means all campaign plugged addicted to a hub are in the matching crash domain as thriving as in the same publicize province, which means that devices share the unchanged bandwidth. Hubs operate next to the physical layer of the OSI model.
IP ADDRESSING
An IP address is a numeric identifier assigned to apiece structure by an IP network. It designates the certain scene of a device on the network. An IP address is a software address and designed to allow host resting on one meet people to publicize with a host resting on a discrete network anyway of the type of LANs the hosts are participating in.
IP TERMINOLOGIES
Bit: A bit is one numeral, whichever a 1 or a 0.
Byte: A byte is 7 otherwise 8 bits, depending by whether parity is used.
Octet: An octet, complete up of 8 bits is immediately an ordinary 8 tad twofold amount. In a large amount gear byte and octet are completely interchangeable.
Network address: This is the designation worn in routing to send packets to a faraway set of contacts. In support of example 10.0.0.0, 172.16.0.0, and 192.168.10.0 are network addresses.
Broadcast address: The address used by applications and hosts to transmit in sequence to all nodes on a network is called the publicize lecture to. Examples contain 255.255.255.255 which is all networks, each and every one nodes; 172.16.255.255, which is all subnets and hosts on group 172.16.0.0.
HEIRARCHICAL IP ADDRESSING SCHEME
An IP address consists of 32 bits of information (IPV4). IPV6, a new version of IP consists of 128 bits of information. The 32 bits IP is alienated keen on four sections referred to as octet otherwise bytes each containing 1 byte (8bits).
An IP address is depicted by any of these 3 methods.
Dotted decimal, as in 172.16.30.56
Binary, as in 10101100.00010000.00011110.00111000
Hexadecimal, as in AC.10.1E.38
All this examples symbolize the unchanged IP address. Nevertheless the most frequently old is the dotted decimal. The Windows Registry stores a machine's IP address in hex.
The 32 tad IP address is a structured before hierarchical tackle, as opposite to a categorical non hierarchical lecture to. Although moreover manner of addressing scheme can have been old, hierarchical addressing was selected on behalf of a good raison d'кtre. The advantage of this scheme is that it can sell a corpulent amount of addresses, that is 4.3 billion (a 32 bit address hole with two doable values for each rank that is also 1 or else 0 gives 237, before 4,294,967,296).
The disadvantage of the tedious addressing scheme relates to routing. Proviso all address were unique, every one of routers on the internet would need to amass the address of apiece and every machine taking place the internet. This would achieve useful routing impossible.
NETWORK ADDRESS RANGE
The exchange ideas talk to uniquely identifies each exchange ideas. All machine on the consistent exchange ideas shares that network speak to as part of its IP address. All the rage the IP address of 172.16.30.56, 172.16 is the network address.
The node address is assigned to and uniquely identifies each machine on a network. This number can also be referred to as host address. In 172.16.30.56, 30.56 is the node address. Class A network is used when a small number of networks possessing a very large number of nodes are needed. Class C network is used when numerous networks with a small number of node is needed.
CLASS A ADDRESSES
The first bit of the first byte in a class A network address must always be off or 0. This means a class A address must be between 0 and 127, inclusive.
0xxxxxxx.hhhhhhhh.hhhhhhhh.hhhhhhhh
If we turn the other 7 bits all off and then turn them all on, we'll find the class A range of network addresses.
00000000 = 0
01111111 = 127
Class A format is network.node.node.node, so for example in the IP address 49.22.102.70, the 49 is the network address and 22.102.70 is the node address. Every machine on this particular network would have the distinctive network address of 49.
CLASS B ADDRESSES
The first bit of the first byte must always be turned on, but the second bit must always be turned off.
01xxxxxx.xxxxxxxx.hhhhhhhh.hhhhhhhh
If we can turn the first bit on and the second bit off and if the other 6 bits all off and then all on, we'll find the class B range of network addresses.
10000000 = 128
10111111 = 191
Class B format is network.network.node.node, so far in the IP address 132.163.40.57, the 132.163 is the network address and 40.57 is the node address.
CLASS C ADDRESSES
The first and second bit of the first byte must always be turned on, but the third bit can never be on.
110xxxxx.xxxxxxxx.xxxxxxxx.hhhhhhhh
If we turn the first and second bit on and the third bit off and then all other 5 bits all off and all on, we'll find the class C range of network address.
11000000 = 192
11011111 = 223
Class C format is network.network.network.node, for example in the IP address 195.166.231.75, the 195.166.231 is the network address and 75 is the node address.
CLASS D AND CLASS E ADDRESSES
The address between 224 and 255 are reserved for class D and E networks. Class D (224-239) is used for multicast addresses and class E (240-255) for scientific purposes.
PRIVATE IP ADDRESSES
Private IP addresses are those that can be used on a private network, but they're not routable through the internet. This is designed for the purpose of creating a measure of well-needed security, but it also conveniently saves valuable IP address space. If every host on every network had to have real routable IP addresses, we would have run out of IP addresses to hand out years ago.
Class A 10.0.0.0 through 10.255.255.255
Class B 172.16.0.0 through 172.31.255.255
Class C 192.168.0.0 through 192.168.255.255
TROUBLESHOOTING IP ADDRESSING
Here are the troubleshooting steps in resolving a problem on an IP network.
1. Open a DOS window and ping 127001. This is the diagnostic or loopback address, and if you get a successful ping, your IP stack is considered to be initialized. If it fails, then you have an IP stack failure and need to reinstall TCP/IP on the host.
2. From the DOS window, ping the IP addresses of the local host. If that's successful, then your Network Interface Card (NIC) card is functioning. If it fails, then there is a problem with the NIC card. This doesn't mean that a cable is plugged into the NIC, only that the IP protocol stack on the host can communicate to the NIC.
3. From the DOS window, ping the default gateway. If the ping works, it means that the NIC is plugged into the network and can communicate on the local network. If it fails, then you have a local physical network problem that could be happening anywhere from the NIC to the gateway.
4. If steps 1 through 3 were successful, try to ping the remote server. If that works then you have IP communication between then local host and the remote server, you also know that the remote physical network is working.
5. If the user still can't communicate with the server after steps 1 through 4 were successful, then there's probably a resolution problem and there is need to check the Domain Name Server (DNS) settings.
NETWORK ADDRESS TRANSLATION
Network Address Translation (NAT) is used mainly to translate private inside addresses on a network to a global outside address. The main idea is to conserve internet global address space, but it also increases network security by hiding internal IP addresses from external networks.
TABLE 3: NAT ADVANTAGES AND DISADVANTAGES
ADVANTAGES
Conserves legally registered addresses.
Reduces address overlap occurrence.
Increases flexibility when connecting to internet.
Eliminates address renumbering as network changes.
Translation introduces switching path delays
DISADVANTAGES
Loss of end-to-end traceability
Certain applications will not function with NAT enabled.
TYPES OF NAT
Static NAT: This type of NAT is designed to allow one-to-one mapping between local and global addresses. Static NAT requires that there is one real internet IP address for every host on your network.
Dynamic NAT: This version gives one the ability to map an unregistered IP address to a registered IP address from out of a pool of registered IP addresses.
Overloading: This is also known as Port Address Translation (PAT). It is the most popular type of NAT configuration. Overloading is a form of dynamic NAT that maps multiple unregistered IP address to a single registered IP address by using different ports. With overloading thousands of users can connect to the internet using only one real global IP address.
NAT TERMINOLOGIES Local addresses: Name of local hosts before translation.
Global addresses: Name of addresses after translation.
Inside local: Name of inside source address before translation.
Outside local: Name of destination host before translation.
Inside global: Name of inside hosts after translation
Outside global: Name of outside destination host after translation.
LAYER2 SWITCHING
Layer2 switching is the process of using the hardware address of devices on a LAN to segment a network. The term layer2 switching is used because switches operate on the data-link layer which is the second layer of the OSI reference model.
Layer2 switching is considered hardware-based bridging because it uses specialized hardware called an application-specific integrated circuit (ASIC). ASICs can run up to gigabit speeds with very low latency rates.
Switches read each frame as it passes through the network, the layer2 device then puts the source hardware address in a filter table and keeps track of which port the frame was received on. The information (logged in the switch's filter table) is what helps the machine determine the location of a specific sending device. After a filter table is built on the layer2 device, it will only forward frames to the segment where the destination hardware is located. If the destination device is on the same segment as the frame, the layer2 device will block the frame from going to any other segments. If the destination is on a different segment, the frame can only be transmitted to that segment. This is called TRANSPARENT BRIDGING.
When a switch interface receives a frame with a destination hardware address that isn't found in the device filter table, it will forward the frame to all connected segments. If the unknown device that was sent the frame replies to this forwarding action, the switch updates its filter table regarding that device's location.
ADVANTAGES OF LAYER2 SWITCHING
The biggest benefit of LAN switching over hub-centred implementations is that each device on every segment plugged into a switch can transmit silmatenously whereas hubs only allow one device per network segment to communicate at a time.
Switches are faster than routers because they don't take time looking at the Network layer header information. Instead, they look at the frame's hardware address before deciding to either forward the frame or drop it.
Switches create private dedicated collision domains and provide independent bandwidth on each port unlike hubs. The figure below shows five hosts connected to a switch, all running 10Mbps half-duplex to the server. Unlike the hub, each host has 10Mbps dedicated communication to the server.
LIMITATIONS OF LAYER2 SWITCHING
Switched networks break up collision domains but the network is still one large broadcast domain. This does not only limits your network's size and growth potential, but can also reduce its overall performance.
FUNCTIONS OF LAYER2 SWITCHING
There are three distinct functions of layer2 switching, these are
Address learning.
Forward/filter decision
Loop avoidance.
ADDRESS LEARNING
When a switch is first powered on, the MAC forward/filter table is empty. When a device transmits and an interface receives the frame, the switch places the frame source address in the MAC forward/filter table, allowing it to remember which interface the sending device is located on. The switch then has no choice but to flood the network with this frame out of every port except the source port because it has no idea where the destination device is actually located.
If a device answers the flooded frame and sends a frame back, then the switch will take source address from that frame and place that MAC address in its database as well, associating this address with the interface that received the frame. Since the switch now has both of the relevant MAC addresses in its filtering table, the two devices can now make a point to point connection. The switch doesn't need to flood the frame as it did the first time.
If there is no communication to a particular address within a certain amount of time, the switch will flush the entry from the database to keep it as up to date as possible.
FORWARD/FILTER DECISIONS
When a frame arrives on a alter crossing point, the destination hardware address is compared to the forward/filter MAC database. Qualification the destination hardware address is recognized and listed in the database, the frame is sent made known only the correct exit interface.
The switch doesn't transmit the frame outdated several crossing point but for the destination interface. This preserves bandwidth by the other exchange ideas segments and is called Set up FILTERING.
LOOP AVOIDANCE
When two switches are joined collected, disused relatives connecting the switches are a sunny clue because they help preclude finish meet people failures in the event one bond stops working.
Redundant associations are particularly effective excluding they often initiate extra tribulations than they solve, this is because frames can be present flooded down every unneeded relations silmatenously creating network loops.
Switches use a protocol called STP (Spanning Tree Protocol) twisted by Digital Utensils Corporation (DEC) instantly Compaq to prevent network loops by end down unneeded links. Amid STP running, frames will be present forwarded only resting on the premium STP-picked link.
CONFIGURING THE CISCO 2950 CATALYST SWITCH FAMILY.
The 2950 alter is one of the Cisco Catalyst switch family's high-end exemplary. The 2950 comes in a lot of flavours and run 10Mbps all the way positive to 1Gbps switched ports with also twisted-pair otherwise fibre. They can impart straightforward data, videotape and assert services.
2950 Swop STARTUP
When the 2950 switch is first powered taking place, it runs through a Power-on-Self-test (POST). By the side of first every harbor LEDs are green, and if upon completion the send determines that all ports are in clear have an effect on, each and every one the LEDs blink and next turn inedible. Excluding proviso the POST finds a port that has futile both the system's LED and the port's LEDs become amber.
However, unlike a router, the alter is actually usable in Fresh-out-of-the-box prepare. You can a minute ago sell the switch keen on your network and connect set of contacts segment collectively with no some configuration.
To join to the Cisco alter, application a rolled Ethernet cable to connect a host to a alter console run exchange of ideas port. Just the once you have the truthful cable linked from your PC to the Cisco alter, you can start HyperTerminal to create a console bond and configure the device as follows:
1. Open HyperTerminal by clicking on start off badge and then Every one programs, so therefore Frills, next Communication, at that moment click by HyperTerminal. Pierce a name for the connection. It is inappropriate what you name it. At that moment click OK.
2. Choose the communication port also COM1 otherwise COM2, whichever is untie taking place your PC.
3. Now next to the port settings. The default principles (2400bps and no run dictate hardware) will not do, you must obstinate the port settings as shown in the figure below.
Notice that the bit rate is set to 9600 and the arise control is set to none. At this point click Satisfactory and prosecute the Write register, and you should live connected to your Cisco alter console port.
Here's the 2950 switch's initial output:
--- Usage Configuration Dialog ---
Would you comparable to enter the initial configuration dialog? [Yes/no]: no
Press RETURN to get started!
00:04:53: %LINK-5-CHANGED: Interface Vlan1, changed state to administratively down
00:04:54: %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan1, changed state to down Switch>
THE CONFIGURATION
The switch> prompt is called the user exec mode and it's mostly used to view statistics. You can only view and change configuration of a Cisco switch in privileged exec mode which you get into with the enable command.
Switch>
Switch> enable
Switch#
Switch# disable
Switch>
The global configuration mode can be entered from the privileged mode by using the configure terminal command or config t for short. Switch# config t Enter the configuration commands, one per line, End with CNTL/Z. Switch(config)# hostname zenith Zenith(config)#
The hostname command is used in naming the switch. The hostname of a switch is only locally significant but it's still helpful to set a hostname on a switch so that you can identify the switch when connecting to it.
SETTING THE ENABLE MODE PASSWORDS AND LINE PASSWORD.
Zenith> enable
Zenith# config t
Enter the configuration commands, one per line, End with CNTL/Z.
Zenith(config)# enable password bank
Zenith(config)# enable secret middle
The enable password bank command sets the enable password as bank and the enable secret middle command sets the enable secret password as middle. The enable secret password is more secure and it supersedes the enable password if it is set. The enable secret password and the enable password cannot be the same on the 2950 switch.
Zenith(config)# line ?
First line number
console Primary terminal line
vty Virtual terminal
Zenith(config)# line vty ?
First line number
Zenith(config)# line vty 0 15
Zenith(config-line)# login
Zenith(config-line)# password alex
Zenith(config-line)# line con 0
Zenith(config-line)# login
Zenith(config-line)# password malouda
Zenith(config-line)# exit
Zenith(config)# exit
Zenith#
The line vty 0 15, login and password alex commands set the telnet password to alex and the line con 0, login, and password malouda commands sets the console password to malouda.
SETTING IP INFORMATION
You don't have to set any IP configuration on the switch to make it work. You can just plug it in. But there are two reasons we set IP address information on the switch.
To manage the switch via Telnet or other management software.
To configure the switch with different VLANs and other network functions.
Zenith(config)# int vlan 1
Zenith(config-if)# ip address 172.16.10.17 255.255.255.0
Zenith(config-if)# no shutdown
Zenith(config-if)# exit
Zenith(config)# ip default-gateway 172.16.10.1
Zenith(config)#
The IP address is set to 172.16.10.17 and the no shutdown command must be applied to enable the interface.
CONFIGURING INTERFACE DESCRIPTIONS
You can administratively set a name for each interface on the switches with the description command.
Zenith(config)# int fastethernet 0/ ?
FastEthernet Interface number.
Zenith(config)# int fastethernet 0/1
Zenith(config-if)# description Sales LAN
Zenith(config-if)# int f0/12
Zenith(config-if)# description Connection to Mail server
Zenith(config-if)# CNTL/Z Zenith#
You can look at the descriptions at any time with either the show interface command or the show running-config command from the global configuration mode.
ERASING AND SAVING THE SWITCH CONFIGURATION Zenith# copy running-config startup-config Zenith# erase startup-config
The first command copies the configuration into the NVRAM (Non-volatile RAM) while the erase startup-config command erases the switch configuration.
Zenith# erase startup-config
Erasing the nvram filesystem will remove all files! Continue? [confirm] [Enter]
[OK]
Erase of nvram: complete
Zenith#
VIRTUAL LAN (VLAN)
A Virtual LAN (VLAN) is a logical grouping of network users and resources connected to administratively defined ports on a switch. When one create VLANs, one creates smaller broadcast domains within a switched internetwork by assigning different ports on the switch to different subnetworks. A VLAN is treated like its own subnet or broadcast domain, which means that frames broadcast onto the network are only switched between ports logically grouped within the same VLAN. By default, no hosts in a specific VLAN can communicate with any other hosts that are members of another VLAN. 5.1 ADVANTAGES OF VLAN
A group of users needing security can be put into a VLAN so that no user outside the VLAN can communicate with them.
As a logical grouping of users by function, VLANs can be considered independent from their physical or geographical locations.
VLANs can enhance network security.
It can block broadcast storms caused by a faulty NIC (Network Interface Card) card.
VLANs increase the number of broadcast domains while decreasing their sizes.
VLAN MEMBERSHIP
VLANs are usually created by the administrator, who then assigns switch ports to each VLAN. Such a VLAN is called a static VLAN. If the administrator wants to do a little more work up front and assign all the host devices hardware addresses into a database, then the switch can be configured to assign VLANs dynamically whenever a host is plugged into a switch. This is called dynamic VLAN.
STATIC VLANs
Static VLANs are the usual way of creating VLANs, and they're also the most secure. The switch port that you assign a VLAN association to always maintain that association until an administrator manually changes that port assignment.
DYNAMIC VLANs
A dynamic VLAN determines a node's VLAN assignment automatically. Using intelligent management software, you can base assignment on hardware addresses, protocols, or even applications to create dynamic VLANs.
An example is the VLAN Management Policy Server (VMPS) service used to set up a database of MAC addresses that can be used for dynamic addressing of VLANs. A VMPS database maps MAC addresses to VLANs.
FRAME TAGGING
As frames are switched through the network, switches must be able to keep track of all the frames. Frames are handled differently according to the type of link they are traversing. The frame identification method uniquely assigns user defined ID to each frame. This is sometimes referred to as the "VLAN ID".
Each switch that the frame reaches must first identify the VLAN ID from the frame tag, and then it finds out what to do with the frame by looking at the information in the filter table. If the frame reaches a switch that has another trunked link, the frame will be forwarded out the trunk-link port.
Once the frame reaches an exit to an access link matching the frame's VLAN ID, the switch removes the VLAN identifier. This is so the destination device can receive the frame without having to understand their VLAN identification.
There are two different types of links in a switched environment, they are: Access links: This type of link is only part of one VLAN. Any device attached to an access link is unaware of a VLAN membership; the device just assumes its part of a broadcast domain. Access link devices cannot communicate with devices outside their VLAN unless the packet is routed. Trunk links: Trunk links can carry multiple VLANs. A trunk link is a 100 or 1000Mbps point to point link between two switches, between a switch and server. These carry the traffic of multiple VLANs from 1 to 1005 at a time. Trunking allows you to make a single port part of multiple VLANS at the same time. It also allows VLANs to span across multiple switches.
VLAN IDENTIFICATION METHODS
There are basically two ways of frame tagging.
Inter-Switch Link (ISL)
IEEE 802.1Q
The main purpose of ISL and 802.1Q frame tagging methods is to provide interswitch VLAN communication.
Inter-switch Link (ISL) Protocol: This is proprietary to Cisco switches, and it is used for fast Ethernet and gigabit Ethernet links only. ISL routing can be used on a switch port, router interfaces and server interface cards to trunk a server.
IEEE 802.1Q: Created by the IEEE as a standard method of frame tagging, it isn't Cisco proprietary so if you're trunking between a Cisco switched link and a different brand of switch; you have to use 802.1Q for the trunk link to work.
VLAN TRUNKING PROTOCOL (VTP)
This protocol was created by Cisco but it is not proprietary. The basic goals of VLAN Trunking protocol (VTP) are to manage all configured VLANs across a switched internetwork and to maintain consistency through the network. VTP allows an administrator to add, delete and rename VLANs on a switch, information that is then propagated to all other switches in the VTP domain.
Before one can get VTP to manage VLANs across the network, one has to create a VTP server. All switches sharing the same VLAN information must be in the same VTP domain.
One can use a VTP domain if there is more than one switch connected in a network, but if all the switches are in only one VLAN, there is no need to use VTP. VTP information is set between switches via trunk port.
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