LAN (Local Area Network): Mei 2011

Minggu, 29 Mei 2011

VoIP is a time sensitive technology

VoIP is a time sensitive technology. Calls must be set up and authenticated, and voice packets must arrive at their destination without interruption and on time. This requires a near continuous network stream, uninterrupted by less sensitive data transmissions. The implementation of Quality of Service techniques on wired LANs assure that these voice packets receive priority, and call quality issues such as latency, jitter, and packet loss have been sufficiently addressed.

Enter the standards based wireless network, a technology in an earlier stage of development, and more challenges occur. While today's wired network provides plenty of bandwidth for both voice and data to coexist, WLANs provide less bandwidth, and Quality of Service issues must be revisited. Security measures such as authentication and encryption must be implemented and can add to the problem by increasing the size of the voice packet. Additionally, users on the move will traverse wireless access points where handoffs must be quick and smooth.

Companies wishing to implement wVoIP must take security issues into consideration from the start. As in any IP network, the dangers of hackers, denial of service, highjacking and spam, all lurk in the shadows.

Because a wireless network uses radio frequencies as its transmission media, the security normally provided by a firewall in a wired network is not sufficient, simply because of the physics. Whereas to break into a wired LAN requires hackers to either physically be inside the network or to hack in through the Internet, in a WLAN they can grab network transmissions from the air while parked across the street. The security issues that network managers must consider in a VoWLAN are the privacy of conversations, and the protection of the network infrastructure.

For WiFi networks, security has had a shaky start with the implementation of WEP as its security mechanism. WEP provides for authentication and encryption between the user and the access point, and was found to be easily hacked. The 802.11i standard, adopted as WPA2 (Wireless Protected Access), provides for more robust security by requiring two way authentication between the user and the network, and uses AES (Advanced Encryption Standard) as its encryption engine.

As network managers plan the rollout of a wireless VoIP network, the greatest security threat they face is improper implementation. Building security into the design of the initial deployment can, and should affect the network topology, as well as material costs. Failure to do so could lead to further expenses in loss of services and network redesigns in the event of compromise.

Jumat, 27 Mei 2011

Architectural Model of the ATM System

Architectural Model of the ATM System

Multiprocessor architecture model

The model is the simplest ATM system is multiprocessor systems where the system consists of a number of processes that can run on multiple processors do not have to separate. This model is common in large real time systems. This Sistemsitem gather information, make decisions using this information, then sends a modified signal to the actuator system environment. The logic of the process associated with gathering information, decision-making and control actuators can be run on a processor with penjadual handled. Users lot of processors are useful for improving the performance and flexibility of the system. The distribution process can be determined prior to the processor. Design approach for this type of system is basically the approach used for real-time traffic control system example.
Client-server architecture model

Client and server are different processes, the client receives services from the server and not from other clients, the server can act as a client to receive services from another server but did not request service from the client, the client must know how to contact serverserver this. Client-server system design should reflect the logical structure being developed.

Kind of model client-server architecture client-server architecture model has two models:
Thin-client model

In thin-client model all processing and data management applications performed on the server. Client is responsible for running the presentation software.

implement the software on the client application logic and interaction with the user model fatclient

Distributed object architecture model of the more common approach for a distributed system is to eliminate the difference between client and server and designing the system architecture as a distributed object architecture.

Excess model of distributed object architecture

Excess model of distributed object architectures, among others:

• The model allows the system designer to delay decisions on where and how services should be provided.

• This model is a very open architecture that allows new resources be added if necessary.

• This system freksibel and scalable. The events of different systems the same services provided by different objects or a replicated object can be created to handle different system loads. New object can be added with increasing system load, without disturbing other system objects.

• Dynamically Reconfiguring the system will allow to immigrate across the network object bilaman required.
The weakness of distributed object architecture model

The weakness of this distributed system model is primarily designed architecture is difficult compared to client-server system.
Model CORBA (Common Object Request Broker Architecture)

This model for distributed object architecture implimentasikan require middleware to handle communication between distributed objects. In principle, the objects in the system can be implemented using different programming languages, can run on different platforms and his name does not need to know all the other objects on the system.

ATM (asynchronous transfer mode) is a dedicated-connection switching technology

ATM (asynchronous transfer mode) is a dedicated-connection switching technology that organizes digital data into 53-byte cell units and transmits them over a physical medium using digital signal technology. Individually, a cell is processed asynchronously relative to other related cells and is queued before being multiplexed over the transmission path.

Because ATM is designed to be easily implemented by hardware (rather than software), faster processing and switch speeds are possible. The prespecified bit rates are either 155.520 Mbps or 622.080 Mbps. Speeds on ATM networks can reach 10 Gbps. Along with Synchronous Optical Network (SONET) and several other technologies, ATM is a key component of broadband ISDN (BISDN).

The protocol for classical IP over ATM (sometimes abbreviated as CLIP/ATM) is a well-established standard spelled out in RFC 1577 and subsequent documents. Windows 2000 provides a full implementation of this standard.

The IP over ATM approach provides several attractive advantages over ELAN solutions. The most obvious advantages are its ability to support QoS interfaces, its lower overhead (as it requires no MAC header), and its lack of a frame size limit. All of these features are discussed in the following sections.
IP over ATM Architecture

IP over ATM is a group of components that do not necessarily reside in one place, and, in this case, the services are not usually on an ATM switch. In some cases, switch vendors provide some IP over ATM support, but not always. (For the purposes of this discussion, it is assumed the IP over ATM server services reside on a Windows 2000 server.)

The core components required for IP over ATM are roughly the same as those required for LANE, as both approaches require the mapping of a connectionless medium to a connection-oriented medium, and vice versa. In IP over ATM, these services are provided by an IP ATMARP server for each IP subnet. This server maintains a database of IP and ATM, and provides configuration and broadcast services, as described in the following section.
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IP over ATM Components

IP over ATM is a very small layer between the ATM protocol and the TCP/IP protocol. As with LANE, the client emulates standard IP to the TCP/IP protocol at its top edge while simultaneously issuing native ATM commands to the ATM protocol layers underneath.

IP over ATM is often preferred to LANE because it is faster than LANE. One key reason for this performance advantage is that IP over ATM adds almost no additional header information to packets as they are handed down the stack. Once it has established a connection, the IP over ATM client can generally transfer data without modification.

As with LANE, IP over ATM is handled by two main components: the IP over ATM server and the IP over ATM client. The IP over ATM server is composed of an ATMARP server and Multicast Address Resolution Service (MARS). The ATMARP server provides services to map network layer IP unicast addresses to ATM addresses, while MARS provides similar services for broadcast and multicast addresses. Both services maintain IP address databases just as LANE services do.

The IP over ATM server can reside on more than one computer, but the ATMARP and MARS databases cannot be distributed. You can have one IP over ATM server handle ATMARP traffic, and one handle MARS. If, however, you divided the ATMARP Server between servers, it would effectively create two different IP networks. All IP over ATM clients in the same logical IP subnet (LIS) need to be configured to use the same ATMARP server. Traditional routing methods are used to route between logical IP subnets, even if they are on the same physical network.

Windows 2000 includes fully integrated ATMARP and MARS servers. These services are described in more detail in the following sections.
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ATMARP Server

The IP over ATM client and ATMARP server go through a process similar to the LANE client and the LECS when a client joins the network and discovers other network members. As with LANE, once an address is found, native ATM takes over and TCP/IP packets are sent across a VC from endstation to endstation. There is, however, a major difference in how the IP over ATM client discovers the ATMARP server.
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ATMARP Server Discovery

Because the ATMARP server usually resides on a server rather than on an ATM switch, it is not possible to use ILMI or a well-known VC to discover its address. In fact, there is no default IP over ATM mechanism for server discovery. To start using IP over ATM, an administrator must find the ATM address of the appropriate ATMARP server and manually configure each IP over ATM client with this address. In a single ATM switch network, this is not much of a problem, but in larger networks it can become a demanding job. To ease configuration in smaller networks, Windows 2000 ATM ARP/MARS services and ATM ARP/MARS clients use a default address. For more information about deployment issues, see Windows 2000 Server Help.

Kamis, 26 Mei 2011

VLAN is a network model that is not limited to physical locations

VLAN is a network model that is not limited to physical locations

such as LAN, this resulted in a network can be configured

virtually without having to obey the physical location of equipment. The use of VLANs will

make arrangements to be highly flexible network which can be made

segments that depend on the organization or department, without relying on

location of the workstation as shown below
Image Network VLAN
[Switch] - [1] - [3] - [2]
|
[X] - [switch] - [3] - [1] - [1]
|
[Switch] - [2] - [3] - [1]

[X] = router [1] = pc including lan 1; [2] = lan 2; [3] = lan 3

HOW TO WORK VLAN

VLANs are classified based on the method (type) used for

classify, either use ports, MAC addresses etc.. All

information containing the marking / addressing a vlan (tagging)

stored in a database (table), if the marking on the basis

port is used then the database should indicate the ports

used by VLANs. To set the commonly used

switch / bridge is manageable or that can be set. Switch / Bridge

this is responsible for storing all the information and configuration

a VLAN and certainly all the switches / bridge has the same information.

Switch to determine where the data will be forwarded, and so forth.

or can be used in a software addressing (bridging software)

which serves to note or mark of a VLAN and workstations

didalamnya.untuk connecting inter-VLAN router required.
VLAN TYPE TYPE
Membership in a VLAN can be classified based on the port

that is in use, the MAC address, protocol type.
1. Based on the Port
Membership in a VLAN based on the port that is in use by

These VLANs. For example, the bridge / switch with 4 ports, ports 1, 2,

and 4 is the third port VLAN 1 is owned by the VLAN 2, see table:
Table port and VLAN
Port 1 2 3 4
VLAN 2 2 1 2

The downside is that users are not able to move move, if necessary

move the network administrator must configure again.
2. Based on MAC Address
Membership of a VLAN based on MAC address of each workstation

/ Computer owned by the user. Switch to detect / record of all MAC

addresses owned by each Virtual LAN. MAC address is a

part owned by the NIC (Network Interface Card) on each workstation.

The surplus, if a user moves to move then he will remain configured

as a member of VLAN tersebut.Sedangkan shortcomings that each machine

must be configured manually, and to a network that has

hundreds of workstations then this type of less efissien to be done.
MAC address and VLAN Table
MAC address 132516617738 272389579355 536666337777 24444125556
VLAN 1 2 2 1

3. Based on the type of protocol used

VLAN Membership can also be based on the protocol used, see table
Table Protocol and VLANs
Protocol IP IPX
VLAN 1 2

4. Based on IP Subnet Address

Subnet IP address on a network can also be used to classify

a VLAN
Table IP subnet and VLAN

IP subnet 22.3.24 46.20.45

VLAN 1 2

This configuration is not related to routing in the network and also not

router.IP funggsi disputed address is used to map membership

VLAN.Keuntungannya a user does not need to re-configure the address

on the network when on the move, it's just because of working in layers over

high it will be slightly slower to forward packets in the appeal

using MAC addresses.
5. Based on applications or other combinations

It is possible to specify a VLAN based on the application

executed, or a combination of all types above to be implemented on a

network. For example: application FTP (file transfer protocol) used bias only

by VLAN 1 and Telnet can only be used on VLAN 2.
BASIC DIFFERENCES BETWEEN LAN and VLAN
The difference is very clear from the network model with a Local Area Network

Virtual Local Area Network is that form networks with local models

Area network is very dependent on location / physical from the workstation, and

the use of hubs and repeaters as a network device that has some

weakness. While that was one of the advantages of the network model

with VLANs is that each workstation / user that joined in

one VLAN / parts (organizations, groups, etc.) can stay in touch

although physically separate. Or more clearly we will be able to

see differences in LAN and VLAN on the picture below.
Fig LAN configuration

[Hub] - [1] - [1] - [1] <- lan 1/di 1st floor
|
[X] - [hub] - [2] - [2] - [2] <- lan 2/di 2nd floor
|
[Hub] - [3] - [3] - [3] <- lan 3/di 3rd floor

Figure VLAN configuration

[Switch] - [1] - [3] - [2]
|
[X] - [switch] - [3] - [1] - [1]
|
[Switch] - [2] - [3] - [1]

[X] = router [1] = pc including lan 1; [2] = lan 2; [3] = lan 3

It seems clear VLAN has changed the physical limitations that have been unable to

addressed by the LAN. These advantages are expected to provide

easiness both technically and operationally.

COMPARISON AND LAN VLAN
A. Comparison of Security Levels
The use of LAN has enabled all computers connected in a network

can exchange data or other related words. This cooperation is increasingly

grown from just the exchange of data through the use of shared equipment

(Also called resource sharing or hardware-sharing) .10 LAN enables data

scattered broadcast throughout the network, this will lead to easy

User unknown (unauthorized users) to be able to access all

part of the broadcast. The greater the broadcast, the greater access

obtained, unless the hub is used given the security control functions.
VLAN that is the result of the switch configuration causes each switch port

applied belongs to a VLAN. Therefore be in one segment,

ports in the shelter under a VLAN can communicate with each other directly.

While the ports are outside VLAN or are in

auspices of another VLAN, can not communicate with each other directly because the VLAN is not

forward the broadcast.
VLAN that has the ability to provide additional benefits in

it does not provide a sharing of network security / use of media / data

within an overall network. Switch on the network created

boundaries that can only be used by the computer included in

These VLANs. This resulted in an administrator can easily

user segment, especially in the use of media / data

confidential information (sensitive information) to all network users

physically incorporated.
Security provided by VLANs although better than the LAN, not to guarantee

overall network security and are also not considered sufficient

to overcome all security problems. VLANs are still in great need

various additional to improve the security of the network itself as

firewalls, user access restrictions perindividu, intrusion detection,

controlling the number and size of broadcast domains, network encryption, etc..
Support better security level of this LAN can

used as an added value from the use of VLANs as a network system.

One of the advantages provided by the use of VLANs is the control

administration is centralized, meaning that the application of the management VLAN

configured, managed and monitored centrally, a broadcast control

network, migration plans, additions, changes and access arrangements

specifically into the network and get the media / data that has a function

important in planning and administration within the group all

can be done centrally. With the management control

centrally then the network administrator also can group

VLAN groups based on specific users and ports of the switch

used, set the security level, pick up and spread data

through existing channels, to set up communication through the switch,

and monitor data traffic and bandwidth usage of the current VLAN

through-prone places in the network.

B. Comparison of Efficiency Level
To be able to compare the levels of efficiency it is necessary in

know the advantages provided by the VLAN itself include:
• Improve Network Performance

LANs that use hubs and repeaters to connect the equipment

another computer with a working one physical layer has

weakness, this equipment just to continue the signal without having

knowledge about the destination addresses. This equipment also

has only one collision domain so that if one port

busy then the other ports have to wait. Although the equipment

connected to different ports of the hub.
Ethernet or IEEE 802.3 protocol (commonly used on the LAN) using

mechanism called Carrier Sense Multiple Accsess Collision Detection

(CSMA / CD) is a way in which devices check the network first

first whether there is transmission of data by other parties. If no

transmission of data by other parties that are detected, new data transmission performed.

When there are two data that is sent at the same time,

then there was a collision (collision) data on the network. Therefore

ethernet network is used only for half duplex transmission, ie at

one time can only send or receive only.
Different from the hub which is used in ethernet network (LAN), switches

working on datalink layer has the advantage that each port

within the switch has its own collision domain. Because of

it is therefore often referred to as multiport switch bridge. Switch

have a central translation table that has a list of interpreters to

all ports. Switch to create a safe path from the sender port and

receiver port so that if two hosts are communicating via the

such, they do not interfere with other segments. So if one port

busy, other ports can still function.
Switch allows full-duplex transmission to link to a port where

sending and receiving can be done simultaneously with the use of

point above. Requirements to be able to conduct relations

full-duplex is only one computer or server that can be connected

into one port of the switch. Computers must have a network card

capable of holding full-duflex relations, and collision detection

and loopback must be disabled.
Switch also enables segmentation on the network or

in other words that form the switch was VLAN.Dengan the segmentation

which limits the broadcast channels will result in a VLAN can not

receive and transmit channels broadcast to other VLANs. This is

will significantly reduce the use of broadcast channels as a whole,

reduce bandwidth usage for users, reducing the likelihood

Storms of broadcast (broadcast storms) which can cause

total traffic on computer networks.

The network administrator can easily control the size of the path

broadcast by reducing the size of a broadcast in its entirety,

limit the number of switch ports that are used in a VLAN and number

users who are members of a VLAN.
• Regardless of the Physical Topology
If the number of servers and workstations numerous and are on the floor

and different buildings, as well as with the personnel who are also scattered

in many places, it will be more difficult for network administrators

that use LAN systems to manage, due to the many

all necessary equipment to connect it. Not to mention if

changes in organizational structure which means it will happen a lot

change the location of personnel due to this.
Problems also arise with network users spread

various places meaning lies not in one specific location

physical. LAN which can be defined as a network or network number

computer system that limited the physical location, for example, in one

building, a complex, and some even specify the LAN based on the distance

very difficult to overcome this problem.
While VLAN that gives freedom to the limits for locations

physically by allowing separate workgroup or a different location

building, or scattered to be able to logically connect to the network

although only one user. If the physical infrastructure has

installed, then this is not a problem to add more ports

for the new VLAN if an organization or department expanded and each

parts moved. This provides convenience in terms of transfer of personnel,

and not too difficult to move the existing pralatan

and configuration from one place to device.For users

located different location then the network administrator only needs to

menkofigurasikannya only in one port is incorporated in a single VLAN

allocated to share so that users can work

in the field without thinking about whether he should be in the same room

with colleagues.
This also reduces the cost to build a

new network in the event of a corporate restructuring,

because the LAN more and more the more displacement occurs

need for re-wiring, almost the entire displacement and

changes require reconfiguring hubs and routers.
VLANs provide an effective mechanism to control these changes

and reduce the many costs for the need to reconfigure

hubs and routers. VLAN users can still share a single network

the same address when he remained connected in one port swith

similar although not in one location. Problems in terms of changes

location can be solved by making the computer user's subscribed

into the port on the VLAN and configure the switch on VLAN

them.
• Develop Network Management
VLAN provides convenience, flexibility, and the least cost

issued to build it. VLANs make large networks more

easy to manage because its management VLAN is able to perform

centralized configuration of existing equipment on site

separate. With the ability to configure VLAN

centrally, it is very beneficial for the development of management

network.
With the advantages provided by the VLAN so it's good for

all LAN users to switch to a VLAN. VLAN that is

development of LAN technology is not too much to do

changes, but have been able to provide various additional services

on network technology.

Network Cable Type

Network Cable Type
Lan cable is a transmission medium that connects Ethernet network-2 devices in your computer network. It is very useful if you know better about before you make a lan cable network design. Design a good network cable, a supporting element which makes computer networking lan you will easily maintained and reliable. So the lan cable is very useful once the reality of the network. The following is a type-2 lan cables commonly used in lan network.

Lan cable coaxial

Lan coaxial cable used in Ethernet 10Base2 and 10Base5 a few years ago. 10Base5 refers to the temporary thicknet 10Base2 10Base5 refers to the thinnet since first using lan cable coaxial thicker.

Originally Ethernet networks based on coaxial cable lan which can be stretched to 500 yards in a single segment. Lan coaxial cables are expensive, and only up to a maximum of only 10Mbps speed. Lan coaxial cable is now not popular.

UTP (Unshielded Twisted Pair) and STP (Shielded twisted pair)

There are two types of cable with copper wire is that STP and UTP, but the most popular is the lan cable UTP.

There are two types of cable with copper wire is that STP and UTP, but the most popular is the lan cable UTP.

The above picture shows the detail component of the lan cable UTP and STP.

UTP lan cable is the most popular of 4 pairs of wires wrapped around each other with a special color code standard and insulated with plastic. Levels of UTP cable is indicated by its many winding or pumtiran per inch, low-level attenuation, his lack of interference and crosstalk phenomenon. Maximum length per segment of the lan cable is 100 meters away, if it is longer than 100 meters then you can not guarantee the high level of attenuation. The speed can be achieved is up to 1 Gigabit is the type of lan cable UTP Cat5e, that where the number of torsion or twist of a little more cable pairs per inch and plus a single nylon cable jacket as the insulation. So once again grade of UTP cable is determined by the amount of torsion per inch.

Standard UTP
Lan cable UTP Cat 1, used for telephone network.
Lan cable UTP Cat 2, the maximum speed of 4 Mbps, originally intended to support Token Ring over UTP.
Lan cable Cat 3, with a maximum speed of 10 Mbps. Lan cable can be used to jarigan telephone and UTP lan cable is the choice of the past.
Lan cable UTP Cat 4, the maximum speed is 16 Mbps, faster version of the commonly used Token Ring networking.
Lan cable Cat 5, the maximum speed a Gigabps, very popular for desktop lan cable.
UTP Cat 5e lan cable, with a maximum speed Gigabps, lower emission levels, more expensive than Cat 5 would be great but for Gigabit networks.
Lan cable UTP Cat 6, maximum speed is 1 Gigabps +, intended as a substitute for Cat 5e with the ability to support the speed-2 multigigabit.

Identification UTP

You should be familiar with both to be able to identify cabling is by examining its pin-2. Actually there are two kinds of standards are:

1. T568-A is a lan cable UTP straight through type, both ends of the cable on pin placement-2 RJ-45 connectors are the same.

2. T568-B is a lan cable UTP type of cross-over. You can look closely at these cross-over cable, the couple pins 2 and 6 and pins 1 and 3 pair swap places.

The above picture shows the detail component of the lan cable UTP and STP.

UTP lan cable is the most popular of 4 pairs of wires wrapped around each other with a special color code standard and insulated with plastic. Levels of UTP cable is indicated by its many winding or pumtiran per inch, low-level attenuation, his lack of interference and crosstalk phenomenon. Maximum length per segment of the lan cable is 100 meters away, if it is longer than 100 meters then you can not guarantee the high level of attenuation. The speed can be achieved is up to 1 Gigabit is the type of lan cable UTP Cat5e, that where the number of torsion or twist of a little more cable pairs per inch and plus a single nylon cable jacket as the insulation. So once again grade of UTP cable is determined by the amount of torsion per inch.

Standard UTP
Lan cable UTP Cat 1, used for telephone network.
Lan cable UTP Cat 2, the maximum speed of 4 Mbps, originally intended to support Token Ring over UTP.
Lan cable Cat 3, with a maximum speed of 10 Mbps. Lan cable can be used to jarigan telephone and UTP lan cable is the choice of the past.
Lan cable UTP Cat 4, the maximum speed is 16 Mbps, faster version of the commonly used Token Ring networking.
Lan cable Cat 5, the maximum speed a Gigabps, very popular for desktop lan cable.
UTP Cat 5e lan cable, with a maximum speed Gigabps, lower emission levels, more expensive than Cat 5 would be great but for Gigabit networks.
Lan cable UTP Cat 6, maximum speed is 1 Gigabps +, intended as a substitute for Cat 5e with the ability to support the speed-2 multigigabit.

Identification UTP

You should be familiar with both to be able to identify cabling is by examining its pin-2. Actually there are two kinds of standards are:

1. T568-A is a lan cable UTP straight through type, both ends of the cable on pin placement-2 RJ-45 connectors are the same.

2. T568-B is a lan cable UTP type of cross-over. You can look closely at these cross-over cable, the couple pins 2 and 6 and pins 1 and 3 pair swap places.

Synchronize tools

Rules of use of this cable is as follows, if for connecting two different types of devices, use a lan cable UTP straight-through. Meanwhile, if you connect two similar devices, use a lan cable cross-over.

Fiber optic

Fiber optics is a transmission medium to a standard Ethernet latest in lan cable. The main difference in terms of function between fiber optic cables and electric wires are sebagia follows:
Further distance
Much more expensive
Less magnetic interference, making it safer
Can support speeds up to 10Gigabits

There are two kinds of lan cable in these optical devices:
Multimode (MM), using optical fiber diameter larger
Single mode (SM), using very small diameter optical fiber. This species is very expensive due to more precise fabrication processes. Optic cables can reach much longer than the optical type MM.

Optic connectors

To transmit data via this optic lan cable you need a single optic strand to one direction. You need two optic strand to the second direction of each-2 to send and receive. Connector to each end of the fiber optic is generally like the following picture:

We return to our initial scenario, how to connect each building by using the lan cable based on our knowledge of the lan cable above? The following figure is a picture of best practice on how to connect two buildings with a lan cable, in the scenario we use lan cable UTP Cat5e outdoor. You can use a crossover UTP lan cable. Crossover cable connected to each other on the trunk ports of switches that will be connected. You need to configure this port to function as a port trunk. For more details see the next article the network configuration.

Drop cable is the cable that connects any computer with a switch. Lan cable should use Cat 5e UTP cable with each end-2 has an RJ-45. Lan cable is 0.6 meters minimum and maximum is 100 meters.

How is the configuration that best practice is more popular in computer networks to interconnect computers with this switch? The following figure is a simple description of how to connect the lan cable between the switches with a computer in your network.

Wall jack is a kind of circuit points with which we often find in the phone, so the network could connect the lan cable UTP RJ-45.

Patch cable is a UTP cable segment that is used to connect the network interface card into the wall jack or to connect the other part-2 of this network cable installation.

Patch panel is a panel interface that provides multi-channel port-2 cable to the device-2 or other connecting hardware such as switches.

In our scenario, you can apply this method on each of 2 buildings HRD, Mining and Workshop. So to facilitate this lan cable network maintenance if there is a problem in the future, you should make a sign or numbering to each wall jack to patch panel connect. And also make sure that you have a flat of this numbering system and place it inside the patch panel for easy maintenance if there is a problem in the lan cable network. One more thing to remember is this lan cable is the enemy of rats. Not infrequently the mice devastated your lan cable with a way to bite off. For that you need to avoid this by inserting this lan-2 cable into the duct in such a way that rats can not enter.

Types of VLAN

VLANs can create network segmentation can be made easily for management reasons or for security reasons. VLANs also enable high-density LAN switches are built using the same hardware. Some switches can also interconnect transparently inter-VLAN using VLAN trunking protocol.

In the simple diagram above, the local area network in the segmentation using a switch that supports VLANs. In our previous scenario, local area network at the department of Geology, Accounting and Workshop segmented using VLANs.

Types of VLAN

There are only two types of VLAN possible today, cell-based VLANs and frame-based VLANs.
Cell-based VLANs are used in ATM switched networks with LAN Emulation (or LANE). LANE is used to allow hosts on legacy LAN segments to communicate using ATM networks without having to use special hardware or software modification.
Frame-based VLANs are used in Ethernet networks with frame tagging. The two primary types of frame tagging are IEEE 802.10 and ISL (Inter Switch Link is a Cisco proprietary frame-tagging). Keep in mind that the 802.10 standard makes it possible to deploy VLANs with 802.3 (Ethernet), 802.5 (Token-Ring), and FDDI, but Ethernet is most common.

Local area network providing data transmission functions

Local area network providing data transmission functions through different types of physical networks. Local area network operates at Layer 1 (physical layer) and 2 (data link layer) in the OSI reference model that works in synergy to carry out data communication with the formation of a good design of your network environment. For more details, reference the OSI model this problem you can read more details in my article the other problems the OSI reference model.

Local area network (LAN) consists of computer, network interface card (NIC), networking media, network traffic control devices, tools and other network peripherals. LAN memungginkan a business office using computer technology for efficient sharing, such as files, printers, and allows communication of information such as e-mail, telephone VoIP, Skype, and others-2.

Local Area Network is designed to do the following:
Operates within the limits of geographical area
Allows all users to access a wide bandwidth media
Providing full-time connectivity to local services
Connecting devices to the extent of adjacent-2 media cable / wireless

Local area network consisting of high-speed network infrastrucktur in one single location that is used to transmit application data and other data services. Local area network technology that is widely used on Ethernet technology budget that is used due to cheapness; easy to use and easy in maintenance and its ability to scale up to gigabit-speed network.

What are the network devices used in network infrastructure local area network? network devices that operate at Layer 2 Data Link is a Bridge, Switch and ATM switches. Switch is a switching device is purely working on layer 2 that allows more efficient use of bandwidth Ethernet. The device switches can localize the impact of the collision (collision) and data contention data (data that were all fighting street - mutually salip two-way streets) in a network. This can be achieved by studying the device address (MAC address) dynamically in the local area network and only to deliver a datagram to the address of the device are eligible to receive it - as if the recipient address in a written letter. What about Bridge? Bridge is the original definition of the functions that can be done by the switch. While the ATM switch is a device that has the ability to function ATM switches. Semenetara local area network devices that operate at Layer 1 is the hub or concentrator or repeater.

Routers are network devices

Router

Routers are network devices that are used to divide the protocol to the other network members, with the router then a protocol can be shared to other network devices. Examples of its application is that if we want to divide your IP address to members of the network then we can use this router, the router features is the facility DHCP (Dynamic Host Configuration Procotol), by setting up DHCP, then we can divide the IP Address, other facilities of the Router is the NAT (Network Address Translator) that can allow an IP address or an internet connection be shared to other IP addresses.

for example if on a network device (computer) has the IP address 192.168.0.1, then the other computers to communicate, must be given an IP Address with the Network Identification with the Host Identification 192.168.0 and 2-254, for example 192.168.0.10, 192.168.0.11 and onwards.

Problems will arise when the network device that is connected very much (usually in the top 20 devices), an administrator will be forced to get around to setting up IP addresses for each host, therefore we can use the Router.

Router Types

1. Application Router

2. Router Hardware

3. PC Router

Router application is an application that we can install the operating system pad, so that the operating system will have capabilities such as routers, examples of this application is Winroute, WinGate, SpyGate, WinProxy and others.

Hardware is a hardware router that has the ability sepertiu router, so the hardware can be transmitting or sharing IP addresses and to sharing the IP Address, in practice this hardware router used to share Internet connection on a space or area, an example of this is the access router point, the region can get Ip Address and Internet connection is called the Hot Spot Area.

Router is a PC operating system that has the facility to divide and mensharing IP Address, so if a network device (pc) connected to a computer will be able to enjoy an IP Address or Internet connection that is spread by the Operating System, the example of the operating system that can be used are all client server-based operating systems, such as Windows NT, Windows NT 4.0, Windows 2000 Server, Windows 2003 Server, MikroTik (Linux Based), etc.

The file server is the heart of all series

The file server is the heart of all series. He is computer speed and contain adequate amounts of RAM and a large store room in addition to the rate interface KAD. Operating system software is stored in this computer. Besides, all applications and data files are also stored here.

File servers escort edict relationship between the Nod in the series. For example, the computer will be escorted if we deliver to a single word processors setesen other work, receiving database files from stesen other work orders and store email in the same period. This causes us to need a computer that can store a lot of notice and may with another in a short.

Among the characteristics that need to exist in the file server is:
the rate of micro-processors (eg Pentium)
disk hard that the rate of at least four gigabytes
RAM at least 32 MB
KAD between the rate of advance
additional slot that many
tape unit endorsement (tape back-ups)
RAID (Redundant Array of Inexpensive Disks) to protect data when valid data eror

All computers are concatenated with the file server are called workstations. All computer workstations contain adequate KAD interface series, stuffing circuit and the appropriate cable. Workstations do not need hyper hyper disc cakera leathery or hard because the fail-files may be stored in a file server. Most computers can function as stesen work.
Network Interface Cards - Kad Between Front Series

Network Interface Cards (NIC) is the physical connection between the circuit with stesen computer work. Most NICs are included in the computer at one additional slot. NIC is a determinant for the top speed something series. It is better to use the NIC that the rate used to follow the type series.

Ethernet Cards

Kad was purchased apart. He may be connected with sepaksi cable (coaxial), twisted pair or fiber optics. Depending on the type of connections and ports namely BNC or RJ45 connections. KAD partly contain adequate Ethernet AUI connector. He may be used for cable, couples distracted and gentian to KAD Ethernet fiber. If this fintion used the tool 'transceiver' need to be connected to the stesen work.

Concentrators / Hubs - Leverage

Leverage is a concentrator or connection devices for all serial cables between stesen work, waiter and stuffing. In a star topology, distracted pair cable used to connect with stesen employment and leverage. Hub also is the leverage they are many slots. With the hub we can put a lot of numbers that follow a series Size desired. Half leverage is passive, namely to justify the switching signal from the computer to other computers without any changes. Active leverage will raise alerts when through it from one device to another device. Active concentrator is used as a repeater if you want to separate circuit. The characteristics of leverage are: is based on port 8, 12, or 24 RJ45
used in star or ring topology stringed star (star-wired ring)
sold together stuffing to arrange port
called also as a hub
habit is loaded in a metal box so that may be included along with the internet modem, bridges and routers

Selasa, 24 Mei 2011

Prior to switches

Prior to switches, Hubs were the standard for connecting devices on a local area network (LAN). The problem with hubs was that everything that went through them had to share the bandwidth of the link, bandwidth was wasted because all traffic was sent to all devices, and there were a lot of collisions because the hub didn’t do anything to prevent them. A switch fixes these problems.

ere are some facts about switches that you should know:

Switches work at Layer 2 of the OSI model, not Layer 1 like a hub

Switches switch Ethernet frames

Switches don’t look at IP address information, only Ethernet MAC addresses

Switches keeps a table of all MAC addresses traversing the switch and what port they are on (this table is called the bridge forwarding table or CAM table)

Switches only sends traffic to the devices that are the destination for that traffic, saving bandwidth

Each device connected to the switch gets the full bandwidth of the switch port because the switch prevents collisions

Other important advantages to switches include the "plug and play" element

Other important advantages to switches include the "plug and play" element. Switches can determine ethernet addresses in use on each segment and create a table as signal packets are passed through the switch. Furthermore, they are versatile enough to connect different network types together as with ethernet and fast ethernet as well as networks of the same type.

In fact, there are also no protocol issues with switches since they occupy the same hardware layer as a hub.

So, if a regular copper switch can do all of this, why choose a fiber optic switch? Simply put, there are several more advantages that a fiber optic switch can offer that a copper one cannot. First and foremost, a fiber switch will allow you to harness ALL available bandwidth. Fiber, by definition, increases the bandwidth available for consumption and switches over fiber are no different. Distances are also increased with the use of fiber, so you will be able to send more information farther with the use of an optical switch. Immunity to EMI/RFI disturbance as well as lightning strikes becomes a huge advantage in mission critical applications. In a word, network applications linked with fiber are simply more "secure" than their copper counterparts.

Exactly what kinds of fiber switches are available, and what specifically can they do? There is a fiber optic modular switch available that is amazing in its versatility. In fact, you can have the option of fiber to fiber connectivity, copper to fiber connectivity, or copper to copper connectivity with the option of swapping modules out later as your network changes or grows. Gigabit speeds are also possible with this optical switch. Never have there been more network options available in one package!

What are the specifics? The modular switch is out-fitted with 3 slots in the front where your choice of module slides in. There are two rear slots which provide a place for gigabit modules in copper or fiber.

One front slot module choice consists of 8 ports of 10/100 unshielded twisted pair copper (UTP) with RJ45 connectors. Another module consists of 8 port 100Base Fiber FX in ST and SC connectors with a further choice of multimode or singlemode fiber. It doesn't matter which kind of fiber is installed, this switch will accommodate it!

The back slots may house gigabit copper, gigabit multimode fiber, gigabit singlemode fiber. You can even fully load the switch with all fiber modules to create an all fiber switch. Think of the wealth of permutations this one switch can offer you. Here are a few:
24 ports TX + 2 Gigabit
16 ports TX + 8 FX + 2 Gigabit
8 ports TX + 16 ports FX + 2 Gigabit
24 ports FX + 2 Gigabit

Management provides benefits in many networks

Management provides benefits in many networks. Large networks with mission critical applications are managed with many sophisticated tools, using SNMP to monitor the health of devices on the network. Networks using SNMP or RMON (an extension to SNMP that provides much more data while using less network bandwidth to do so) will either manage every device, or just the more critical areas. VLANs are another benefit to management in a switch. A VLAN allows the network to group nodes into logical LANs that behave as one network, regardless of physical connections. The main benefit is managing broadcast and multicast traffic. An unmanaged switch will pass broadcast and multicast packets through to all ports. If the network has logical grouping that are different from physical groupings then a VLAN-based switch may be the best bet for traffic optimization. Another benefit to management in the switches is Spanning Tree Algorithm. Spanning Tree allows the network manager to design in redundant links, with switches attached in loops. This would defeat the self learning aspect of switches, since traffic from one node would appear to originate on different ports. Spanning Tree is a protocol that allows the switches to coordinate with each other so that traffic is only carried on one of the redundant links (unless there is a failure, then the backup link is automatically activated). Network managers with switches deployed in critical applications may want to have redundant links. In this case management is necessary. But for the rest of the networks an unmanaged switch would do quite well, and is much less expensive.

Switches are the backbone of your LAN

Switches are the backbone of your LAN. Any problem in your switches affects a large proportion of your LAN users. Implementing a proactive switch monitoring system helps you detect problems early and avoid potential problems.

OpManager's switch monitoring functionality automatically discovers switches in your network and places them on a special switch map . All the switch ports are also discovered and intuitively placed on the map.

Using OpManager’s switch monitoring capability, operators can gain visibility into the status and availability of switch ports. OpManager actively monitors switch ports and quickly notifies operators whenever a switch port or the switch goes down. Operators can setup OpManager to monitor only critical ports, an industry best practice for Switch monitoring, that prevents unnecessary alarms from being generated. OpManager also offers visibility into spanning tree status showing which ports are blocked and which ones are forwarding.

Switch and Switch Ports availability monitoring

With OpManager you can create business views (maps) to graphically visualize your entire LAN. OpManager can automatically send alerts when a link goes down.

OpManager’s reporting functionality also provides you with a detailed availability report of your Switches and Switch Ports. You can use these reports to ensure that your SLAs are being met.
Port-wise Traffic Monitoring

OpManager helps you monitor and troubleshoot Switch Ports for traffic, utilization, errors and Service Level Agreement (SLA) verification. By presenting accurate information on port traffic and utilization OpManager helps you identify top talkers on the LAN.
Monitor Port utilization and traffic with threshold alerts.
Detect potential Broadcast Storms and pro–actively prevent the same.
Identify highly utilized and under-utilized ports.
Get alerted when a port start discarding packets

Switch Monitoring Tools

Real Time Switch Monitoring Tools such as Switch Port Mapper and STP Tool are bundled with OpManager.
Switch Port Mapper

The Switch Port Mapper is a useful utility that is embedded in OpManager. It helps you to quickly find out the list of devices connected to the switch ports.
STP Tool

Spanning Tree Protocol details for each port can be viewed using the STP Tool. This gives you valuable information about the spanning tree state of each port such as which ports are blocking and which ports are forwarding etc.

A virtual network

A virtual network switch (also referred to as a virtual switch) is a virtual version of a physical network switch. A virtual network can be configured to provide access to local or external network resources for one or more virtual machines.

When you install Hyper-V and create an external virtual network, the management operating system (sometimes called the parent partition) uses a new virtual network adapter to connect to the physical network. The network connections consist of the original network adapter and the new virtual network adapter. The original physical network adapter does not have anything bound to it.

However, the virtual network adapter has all of the standard protocols and services bound to it.

Hyper-V binds the Virtual Network Service Protocol to a physical network adapter when an external virtual network is created.

A virtual network works just like a physical network except that the switch is software based and ports can be added or removed dynamically as they are needed.

After an external virtual network is configured, all networking traffic is routed though the virtual switch. For this reason, we recommend using at least one additional physical network adapter for managing network traffic. The virtual switch functions as a physical switch would and routes networking traffic through the virtual network to its destination.

Changes in network design

Changes in network design tend to be evolutionary rather than revolutionary-rarely is a network manager able to design a network completely from scratch. Usually, changes are made slowly with an eye toward preserving as much of the usable capital investment as possible while replacing obsolete or outdated technology with new equipment.

Fast Ethernet is very easy to add to most networks. A switch or bridge allows Fast Ethernet to connect to existing Ethernet infrastructures to bring speed to critical links. The faster technology is used to connect switches to each other, and to switched or shared servers to ensure the avoidance of bottlenecks.

Many client/server networks suffer from too many clients trying to access the same server which creates a bottleneck where the server attaches to the LAN. Fast Ethernet, in combination with switched Ethernet, creates the perfect cost-effective solution for avoiding slow client server networks by allowing the server to be placed on a fast port.

Distributed processing also benefits from Fast Ethernet and switching. Segmentation of the network via switches brings big performance boosts to distributed traffic networks, and the switches are commonly connected via a Fast Ethernet backbone.

Routers work in a manner similar to switches and bridges

Routers work in a manner similar to switches and bridges in that they filter out network traffic. Rather than doing so by packet addresses they filter by specific protocol. Routers were born out of the necessity for dividing networks logically instead of physically. An IP router can divide a network into various subnets so that only traffic destined for particular IP addresses can pass between segments. Routers recalculate the checksum, and rewrite the MAC header of every packet. The price paid for this type of intelligent forwarding and filtering is usually calculated in terms of latency, or the delay that a packet experiences inside the router. Such filtering takes more time than that exercised in a switch or bridge which only looks at the Ethernet address but in more complex networks network efficiency is improved. An additional benefit of routers is their automatic filtering of broadcasts, but overall they are complicated to setup.

Ethernet it self is a shared media

Ethernet it self is a shared media, so there are rules for sending packets to avoid conflicts and protect data integrity. Nodes on an Ethernet network send packets when they determine the network is not in use. It is possible that two nodes at different locations could try to send data at the same time. When both PCs are transferring a packet to the network at the same time, a collision will result. Both packets are retransmitted, adding to the traffic problem. Minimizing collisions is a crucial element in the design and operation of networks. Increased collisions are often the result of too many users or too much traffic on the network, which results in a lot of contention for network bandwidth. This can slow the performance of the network from the users point of view. Segmenting, where a network is divided into different pieces joined together logically with switches or routers, reduces congestion in an overcrowded network.

Collision rates measure the percentage of packets that are collisions. Some collisions are inevitable, with less than 10% common in well running networks.

Utilization rate is another widely accessible statistic about the health of a network. This statistic is available in Novell's Console monitor and WindowsNT performance monitor as well as any optional LAN analysis software. Utilization in an average network above 35% indicates potential problems. This 35% utilization is near optimum, but some networks experience higher or lower utilization optimums due to factors such as packet size and peak load deviation.

A switch is said to work at "wire speed" if it has enough processing power to handle full ethernet speed at minimum packet sizes. Most switches on the market are well ahead of network traffic capabilities supporting full "wire speed" of ethernet, 14,480 pps (packets per second).

Switches occupy the same place in the network as hubs

Switches occupy the same place in the network as hubs. Unlike hubs, switches examine each packet and process it accordingly rather than simply repeating the signal to all ports. Switches map the Ethernet addresses of the nodes residing on each network segment and then allow only the necessary traffic to pass through the switch. When a packet is received by the switch, the switch examines the destination and source hardware addresses and compares them to a table of network segments and addresses. If the segments are the same, the packet is dropped ("filtered"); if the segments are different, then the packet is "forwarded" to the proper segment. Additionally, switches prevent bad or misaligned packets from spreading by not forwarding them.

Filtering of packets, and the regeneration of forwarded packets enables switching technology to split a network into separate collision domains. Regeneration of packets allows for greater distances and more nodes to be used in the total network design, and dramatically lowers the overall collision rates. In switched networks, each segment is an independent collision domain. In shared networks all nodes reside in one, big shared collision domain.

Easy to install, most switches are self learning. They determine the Ethernet addresses in use on each segment, building a table as packets are passed through the switch. This "plug and play" element makes switches an attractive alternative to hubs.

Switches can connect different networks types (such as Ethernet and Fast Ethernet) or networks of the same type. Many switches today offer high-speed links, like Fast Ethernet or FDDI, that can be used to link the switches together or to give added bandwidth to important servers that get a lot of traffic. A network composed of a number of switches linked together via these fast uplinks is called a "collapsed backbone" network.

Dedicating ports on switches to individual nodes is another way to speed access for critical computers. Servers and power users can take advantage of a full segment for one node, so some networks connect high traffic nodes to a dedicated switch port.

Full duplex is another method to increase bandwidth to dedicated workstations or servers. To use full duplex, both network interface cards used in the server or workstation, and the switch must support full duplex operation. Full duplex doubles the potential bandwidth on that link, providing 20 Mbps for Ethernet and 200 Mbps for Fast Ethernet.

Function switch

Function switch
The network switch, packet switch (or just switch) plays an integral part in most Ethernet local area networks or LANs. Mid-to-large sized LANs contain a number of linked managed switches. Small office/home office (SOHO) applications typically use a single switch, or an all-purpose converged device such as a gateway access to small office/home broadband services such as DSL router or cable Wi-Fi router. In most of these cases, the end-user device contains a router and components that interface to the particular physical broadband technology, as in Linksys 8-port and 48-port devices. User devices may also include a telephone interface for VoIP.

A standard 10/100 Ethernet switch operates at the data-link layer of the OSI model to create a different collision domain for each switch port. If you have 4 computers (e.g., A, B, C, and D) on 4 switch ports, then A and B can transfer data back and forth, while C and D also do so simultaneously, and the two "conversations" will not interfere with one another. In the case of a "hub," they would all share the bandwidth and run in Half duplex, resulting in collisions, which would then necessitate retransmissions. Using a switch is called microsegmentation. This allows you to have dedicated bandwidth on point-to-point connections with every computer and to therefore run in Full duplex with no collisions.

Switches may operate at one or more OSI layers, including physical, data link, network, or transport (i.e., end-to-end). A device that operates simultaneously at more than one of these layers is known as a multilayer switch.

In switches intended for commercial use, built-in or modular interfaces make it possible to connect different types of networks, including Ethernet, Fibre Channel, ATM, ITU-T G.hn and 802.11. This connectivity can be at any of the layers mentioned. While Layer 2 functionality is adequate for bandwidth-shifting within one technology, interconnecting technologies such as Ethernet and token ring are easier at Layer 3.

Interconnection of different Layer 3 networks is done by routers. If there are any features that characterize "Layer-3 switches" as opposed to general-purpose routers, it tends to be that they are optimized, in larger switches, for high-density Ethernet connectivity.

In some service provider and other environments where there is a need for a great deal of analysis of network performance and security, switches may be connected between WAN routers as places for analytic modules. Some vendors provide firewall, network intrusion detection, and performance analysis modules that can plug into switch ports. Some of these functions may be on combined modules.

In other cases, the switch is used to create a mirror image of data that can go to an external device. Since most switch port mirroring provides only one mirrored stream, network hubs can be useful for fanning out data to several read-only analyzers, such as intrusion detection systems and packet sniffers.

Senin, 23 Mei 2011

Configuring DHCP server ubuntu

This method entails using DHCP to identify the unique hardware address of each network card connected to the network and then continually supplying a constant configuration each time the DHCP client makes a request to the DHCP server using that network device.

Install DHCP server in ubuntu

sudo apt-get install dhcp3-server

This will complete the installation.

Configuring DHCP server ubuntu

If you have two network cards in your ubuntu server you need to select which interface you want to use for DHCP server listening.By default it listens to eth0.

You can change this by editing /etc/default/dhcp3-server file

sudo vi /etc/default/dhcp3-server

Find this line

INTERFACES=”eth0″

Replace with the following line

INTERFACES=”eth1″

Save and exit.This is optional.

Next you need to make a backup copy of /etc/dhcp3/dhcpd.conf file

cp /etc/dhcp3/dhcpd.conf /etc/dhcp3/dhcpd.conf.back

Edit /etc/dhcp3/dhcpd.conf file using the following command

sudo vi /etc/dhcp3/dhcpd.conf

Using address pool method

You need to change the following sections in /etc/dhcp3/dhcpd.conf file

default-lease-time 600;
max-lease-time 7200;

option subnet-mask 255.255.255.0;
option broadcast-address 192.168.1.255;
option routers 192.168.1.254;
option domain-name-servers 192.168.1.1, 192.168.1.2;
option domain-name “yourdomainname.com”;

subnet 192.168.1.0 netmask 255.255.255.0 {
range 192.168.1.10 192.168.1.200;
}

save and exit the file

This will result in the DHCP server giving a client an IP address from the range 192.168.1.10-192.168.1.200 . It will lease an IP address for 600 seconds if the client doesn’t ask for a specific time frame. Otherwise the maximum (allowed) lease will be 7200 seconds. The server will also “advise” the client that it should use 255.255.255.0 as its subnet mask, 192.168.1.255 as its broadcast address, 192.168.1.254 as the router/gateway and 192.168.1.1 and 192.168.1.2 as its DNS servers.

Using MAC address method

This method is you can reserver some of the machines or all the machines with fixed ip address.In the following example i am using fixed ip address for server1,server2,printer1 and printer2

default-lease-time 600;
max-lease-time 7200;

option subnet-mask 255.255.255.0;
option broadcast-address 192.168.1.255;
option routers 192.168.1.254;
option domain-name-servers 192.168.1.1, 192.168.1.2;
option domain-name “yourdomainname.com”;

subnet 192.168.1.0 netmask 255.255.255.0 {
range 192.168.1.10 192.168.1.200;
}

host server1 {
hardware ethernet 00:1b:63:ef:db:54;
fixed-address 192.168.1.20;
}

host server2 {
hardware ethernet 00:0a:95:b4:d4:b0;
fixed-address 192.168.1.21;
}

host printer1 {
hardware ethernet 00:16:cb:aa:2a:cd;
fixed-address 192.168.1.22;
}

host printer2 {
hardware ethernet 00:0a:95:f5:8f:b3;
fixed-address 192.168.1.23;
}

Now you need to restart dhcp server using the following command

sudo /etc/init.d/dhcp3-server restart

Configure Ubuntu DHCP Client

If you want to configure your ubuntu desktop as DHCP client following this procedure

You need to open /etc/network/interfaces file

sudo vi /etc/network/interfaces

make sure you have the following lines (eth0 is an example)

auto lo eth0
iface eth0 inet dhcp
iface lo inet loopback

Save and exit the file

You need to restart networking services using the following command

sudo /etc/init.d/networking restart

.::BY JUMBHO MY AT HOME IN THE JEPARA CITY OF BEAUTIFUL::.

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