Duplex Settings

There are two types of duplex settings used for communications on an Ethernet network: half duplex and full duplex. The figure shows the two duplex settings available on modern network equipment.

Half Duplex: Half-duplex communication relies on unidirectional data flow where sending and receiving data are not performed at the same time. This is similar to how walkie-talkies or two-way radios function in that only one person can talk at any one time. If someone talks while someone else is already speaking, a collision occurs. As a result, half-duplex communication implements CSMA/CD to help reduce the potential for collisions and detect them when they do happen. Half-duplex communications have performance issues due to the constant waiting, because data can only flow in one direction at a time. Half-duplex connections are typically seen in older hardware, such as hubs. Nodes that are attached to hubs that share their connection to a switch port must operate in half-duplex mode because the end computers must be able to detect collisions. Nodes can operate in a half-duplex mode if the NIC card cannot be configured for full duplex operations. In this case the port on the switch defaults to a half-duplex mode as well. Because of these limitations, full-duplex communication has replaced half duplex in more current hardware.

Full Duplex: In full-duplex communication, data flow is bidirectional, so data can be sent and received at the same time. The bidirectional support enhances performance by reducing the wait time between transmissions. Most Ethernet, Fast Ethernet, and Gigabit Ethernet NICs sold today offer full-duplex capability. In full-duplex mode, the collision detect circuit is disabled. Frames sent by the two connected end nodes cannot collide because the end nodes use two separate circuits in the network cable. Each full-duplex connection uses only one port. Full-duplex connections require a switch that supports full duplex or a direct connection between two nodes that each support full duplex. Nodes that are directly attached to a dedicated switch port with NICs that support full duplex should be connected to switch ports that are configured to operate in full-duplex mode.

Standard, shared hub-based Ethernet configuration efficiency is typically rated at 50 to 60 percent of the 10-Mb/s bandwidth. Full-duplex Fast Ethernet, compared to 10-Mb/s bandwidth, offers 100 percent efficiency in both directions (100-Mb/s transmit and 100-Mb/s receive).

key elements ethernet 802.3 networks

In this topic, you will learn about key components of the Ethernet standard that play a significant role in the design and implementation of switched networks. You will explore how Ethernet communications function and how switches play a role in the communication process.

CSMA/CD

Ethernet signals are transmitted to every host connected to the LAN using a special set of rules to determine which station can access the network. The set of rules that Ethernet uses is based on the IEEE carrier sense multiple access/collision detect (CSMA/CD) technology. You may recall from CCNA Exploration: Networking Fundamentals that CSMA/CD is only used with half-duplex communication typically found in hubs. Full-duplex switches do not use CSMA/CD.

Carrier Sense

In the CSMA/CD access method, all network devices that have messages to send must listen before transmitting.

If a device detects a signal from another device, it waits for a specified amount of time before attempting to transmit.

When there is no traffic detected, a device transmits its message. While this transmission is occurring, the device continues to listen for traffic or collisions on the LAN. After the message is sent, the device returns to its default listening mode.

Multi-access

If the distance between devices is such that the latency of the signals of one device means that signals are not detected by a second device, the second device may also start to transmit. The media now has two devices transmitting signals at the same time. The messages propagate across the media until they encounter each other. At that point, the signals mix and the messages are destroyed, a collision. Although the messages are corrupted, the jumble of remaining signals continues to propagate across the media.

Collision Detection

When a device is in listening mode, it can detect when a collision occurs on the shared media, because all devices can detect an increase in the amplitude of the signal above the normal level.

When a collision occurs, the other devices in listening mode, as well as all the transmitting devices, detect the increase in the signal amplitude. Every device that is transmitting continues to transmit to ensure that all devices on the network detect the collision.

Jam Signal and Random Backoff

When a collision is detected, the transmitting devices send out a jamming signal. The jamming signal notifies the other devices of a collision, so that they invoke a backoff algorithm. This backoff algorithm causes all devices to stop transmitting for a random amount of time,  which allows the collision signals to subside.

After the delay has expired on a device, the device goes back into the "listening before transmit" mode. A random backoff period ensures that the devices that were involved in the collision do not try to send traffic again at the same time, which would cause the whole process to repeat. However, during the backoff period, a third device may transmit before either of the two involved in the collision have a chance to re-transmit.

Ethernet Communications

Reference the selected Ethernet Communications area in the figure.

Communications in a switched LAN network occur in three ways: unicast, broadcast, and multicast:

Unicast: Communication in which a frame is sent from one host and addressed to one specific destination. In unicast transmission, there is just one sender and one receiver. Unicast transmission is the predominant form of transmission on LANs and within the Internet. Examples of unicast transmissions include HTTP, SMTP, FTP, and Telnet.

Broadcast: Communication in which a frame is sent from one address to all other addresses. In this case, there is just one sender, but the information is sent to all connected receivers. Broadcast transmission is essential when sending the same message to all devices on the LAN. An example of a broadcast transmission is the address resolution query that the address resolution protocol (ARP) sends to all computers on a LAN.

Multicast: Communication in which a frame is sent to a specific group of devices or clients. Multicast transmission clients must be members of a logical multicast group to receive the information. An example of multicast transmission is the video and voice transmissions associated with a network-based, collaborative business meeting.

Ethernet Frame

The first course in our series, CCNA Exploration: Networking Fundamentals, described the structure of the Ethernet frame in detail. To briefly review, the Ethernet frame structure adds headers and trailers around the Layer 3 PDU to encapsulate the message being sent. Both the Ethernet header and trailer have several sections (or fields) of information that are used by the Ethernet protocol. The figure shows the structure of the current Ethernet frame standard, the revised IEEE 802.3 (Ethernet).

Roll over each field name to see its description.

Preamble and Start Frame Delimiter Fields

The Preamble (7 bytes) and Start Frame Delimiter (SFD) (1 byte) fields are used for synchronization between the sending and receiving devices. These first 8 bytes of the frame are used to get the attention of the receiving nodes. Essentially, the first few bytes tell the receivers to get ready to receive a new frame.

Destination MAC Address Field

The Destination MAC Address field (6 bytes) is the identifier for the intended recipient. This address is used by Layer 2 to assist a device in determining if a frame is addressed to it. The address in the frame is compared to the MAC address in the device. If there is a match, the device accepts the frame.

Source MAC Address Field

The Source MAC Address field (6 bytes) identifies the frame's originating NIC or interface. Switches use this address to add to their lookup tables.

Length/Type Field

The Length/Type field (2 bytes) defines the exact length of the frame's data field. This field is used later as part of the Frame Check Sequence (FCS) to ensure that the message was received properly. Only a frame length or a frame type can be entered here. If the purpose of the field is to designate a type, the Type field describes which protocol is implemented. When a node receives a frame and the Length/Type field designates a type, the node determines which higher layer protocol is present. If the two-octet value is equal to or greater than 0x0600 hexadecimal or 1536 decimal, the contents of the Data Field are decoded according to the protocol indicated; if the two-byte value is less than 0x0600 then the value represents the length of the data in the frame.

Data and Pad Fields

The Data and Pad fields (46 to 1500 bytes) contain the encapsulated data from a higher layer, which is a generic Layer 3 PDU, or more commonly, an IPv4 packet. All frames must be at least 64 bytes long (minimum length aides the detection of collisions). If a small packet is encapsulated, the Pad field is used to increase the size of the frame to the minimum size.

Frame Check Sequence Field

The FCS field (4 bytes) detects errors in a frame. It uses a cyclic redundancy check (CRC). The sending device includes the results of a CRC in the FCS field of the frame. The receiving device receives the frame and generates a CRC to look for errors. If the calculations match, no error has occurred. If the calculations do not match, the frame is dropped.

MAC Address

In CCNA Exploration: Networking Fundamentals, you learned about the MAC address. An Ethernet MAC address is a two-part 48-bit binary value expressed as 12 hexadecimal digits. The address formats might be similar to 00-05-9A-3C-78-00, 00:05:9A:3C:78:00, or 0005.9A3C.7800.

All devices connected to an Ethernet LAN have MAC-addressed interfaces. The NIC uses the MAC address to determine if a message should be passed to the upper layers for processing. The MAC address is permanently encoded into a ROM chip on a NIC. This type of MAC address is referred to as a burned in address (BIA). Some vendors allow local modification of the MAC address. The MAC address is made up of  OUI numbers. Within the OUI, there are 2 bits that have meaning only when used in the destination address, as follows:

Broadcast or multicast bit: Indicates to the receiving interface that the frame is destined for all or a group of end stations on the LAN segment.

Locally administered address bit: If the vendor-assigned MAC address can be modified locally, this bit should be set.

Vendor Assignment Number

The vendor-assigned part of the MAC address is 24 bits long and uniquely identifies the Ethernet hardware. It can be a BIA or modified by software indicated by the local bit.

LOGIC GATE

• Computer system architecture is composed of a series of logic 1 (true) and 0 (false) combined with a number of logic gates are AND, OR, NOT, NOR, XOR, NAND.

• The computer program running on the basic structure of good reasoning from a solution to the problems with the help of the program component that is if-then, if - then-else and other

Access Layer Switch Features

Now that you know which factors to consider when choosing a switch, let us examine which features are required at each layer in a hierarchical network. You will then be able to match the switch specification with its ability to function as an access, distribution, or core layer switch.

Access layer switches facilitate the connection of end node devices to the network. For this reason, they need to support features such as port security, VLANs, Fast Ethernet/Gigabit Ethernet, PoE, and link aggregation.

Port security allows the switch to decide how many or what specific devices are allowed to connect to the switch. All Cisco switches support port layer security. Port security is applied at the access. Consequently, it is an important first line of defense for a network. You will learn about port security in Chapter 2.

VLANs are an important component of a converged network. Voice traffic is typically given a separate VLAN. In this way, voice traffic can be supported with more bandwidth, more redundant connections, and improved security. Access layer switches allow you to set the VLANs for the end node devices on your network.

Port speed is also a characteristic you need to consider for your access ayer switches. Depending on the performance requirements for your network, you must choose between Fast Ethernet and Gigabit Ethernet switch ports. Fast Ethernet allows up to 100 Mb/s of traffic per switch port. Fast Ethernet is adequate for IP telephony and data traffic on most business networks, however, performance is slower than Gigabit Ethernet ports. Gigabit Ethernet allows up to 1000 Mb/s of traffic per switch port. Most modern devices, such as workstations, notebooks, and IP phones, support Gigabit Ethernet. This allows for much more efficient data transfers, enabling users to be more productive. Gigabit Ethernet does have a drawback-switches supporting Gigabit Ethernet are more expensive.

Another feature requirement for some access layer switches is PoE. PoE dramatically increases the overall price of the switch across all Cisco Catalyst switch product lines, so it should only be considered when voice convergence is required or wireless access points are being implemented, and power is difficult or expensive to run to the desired location.

Link aggregation is another feature that is common to most access layer switches. Link aggregation allows the switch to use multiple links simultaneously. Access layer switches take advantage of link aggregation when aggregating bandwidth up to distribution layer switches.
Because the uplink connection between the access layer switch and the distribution layer switch is typically the bottleneck in communication, the internal forwarding rate of access layer switches does not need to be as high as the link between the distribution and access layer switches. Characteristics such as the internal forwarding rate are less of a concern for access layer switches because they only handle traffic from the end devices and forward it to the distribution layer switches.

In a converged network supporting voice, video and data network traffic, access layer switches need to support QoS to maintain the prioritization of traffic. Cisco IP phones are types of equipment that are found at the access layer. When a Cisco IP phone is plugged into an access layer switch port configured to support voice traffic, that switch port tells the IP phone how to send its voice traffic. QoS needs to be enabled on access layer switches so that voice traffic the IP phone has priority over, for example, data traffic.

Switch Features

Switch Form Factors

What are the key features of switches that are used in hierarchical networks? When you look up the specifications for a switch, what do all of the acronyms and word phrases mean? What does "PoE" mean and what is "forwarding rate"? In this topic, you will learn about these features.

When you are selecting a switch, you need to decide between fixed configuration or modular configuration, and stackable or non-stackable. Another consideration is the thickness of the switch expressed in number of rack units. For example, the Fixed Configuration Switches shown in the figure are all 1 rack unit (1U). These options are sometimes referred to as switch form factors.

Fixed Configuration Switches

Fixed configuration switches are just as you might expect, fixed in their configuration. What that means is that you cannot add features or options to the switch beyond those that originally came with the switch. The particular model you purchase determines the features and options available. For example, if you purchase a 24-port gigabit fixed switch, you cannot add additional ports when you need them. There are typically different configuration choices that vary in how many and what types of ports are included.

Modular Switches

Modular switches offer more flexibility in their configuration. Modular switches typically come with different sized chassis that allow for the installation of different numbers of modular line cards. The line cards actually contain the ports. The line card fits into the switch chassis like expansion cards fit into a PC. The larger the chassis, the more modules it can support. As you can see in the figure, there can be many different chassis sizes to choose from. If you bought a modular switch with a 24-port line card, you could easily add an additional 24 port line card, to bring the total number of ports up to 48.

Stackable Switches

Stackable switches can be interconnected using a special backplane cable that provides high-bandwidth throughput between the switches. Cisco introduced StackWise technology in one of its switch product lines. StackWise allows you to interconnect up to nine switches using fully redundant backplane connections. As you can see in the figure, switches are stacked one atop of the other, and cables connect the switches in daisy chain fashion. The stacked switches effectively operate as a single larger switch. Stackable switches are desirable where fault tolerance and bandwidth availability are critical and a modular switch is too costly to implement. Using cross-connected connections, the network can recover quickly if a single switch fails. Stackable switches use a special port for interconnections and do not use line ports for inter-switch connections. The speeds are also typically faster than using line ports for connection switches.

Considerations for Hierarchical Network Switches

Traffic Flow Analysis

To select the appropriate switch for a layer in a hierarchical network, you need to have specifications that detail the target traffic flows, user communities, data servers, and data storage servers.

Companies need a network that can meet evolving requirements. A business may start with a few PCs interconnected so that they can share data. As the business adds more employees, devices, such as PCs, printers, and servers, are added to the network. Accompanying the new devices is an increase in network traffic. Some companies are replacing their existing telephone systems with converged VoIP phone systems, which adds additional traffic.

When selecting switch hardware, determine which switches are needed in the core, distribution, and access layers to accommodate the bandwidth requirements of your network. Your plan should take into account future bandwidth requirements. Purchase the appropriate Cisco switch hardware to accommodate both current needs as well as future needs. To help you more accurately choose appropriate switches, perform and record traffic flow analyses on a regular basis.

Traffic Flow Analysis

Traffic flow analysis is the process of measuring the bandwidth usage on a network and analyzing the data for the purpose of performance tuning, capacity planning, and making hardware improvement decisions. Traffic low analysis is done using traffic flow analysis software. Although there is no precise definition of network traffic flow, for the purposes of traffic flow analysis we can say that network traffic is the amount of data sent through a network for a given period of time. All network data contributes to the traffic, regardless of its purpose or source. Analyzing the various traffic sources and their impact on the network, allows you to more accurately tune and upgrade the network to achieve the best possible performance.

Traffic flow data can be used to help determine just how long you can continue using existing network hardware before it makes sense to upgrade to accommodate additional bandwidth requirements. When you are making your decisions about which hardware to purchase, you should consider port densities and switch forwarding rates to ensure adequate growth capability. Port density and forwarding rates are explained later in this chapter.

There are many ways to monitor traffic flow on a network. You can manually monitor individual switch ports to get the bandwidth utilization over time. When analyzing the traffic flow data, you want to determine future traffic flow requirements based on the capacity at certain times of the day and where most of the data is generated and sent. However, to obtain accurate results, you need to record enough data. Manual recording of traffic data is a tedious process that requires a lot of time and diligence. Fortunately, there are some automated solutions.

Analysis Tools

Many traffic flow analysis tools that automatically record traffic flow data to a database and perform a trend analysis are available. In larger networks, software collection solutions are the only effective method for performing traffic flow analysis. The figure displays sample output from Solarwinds Orion 8.1 NetFlow Analysis, which monitors traffic flow on a network. While the software is collecting data, you can see just how every interface is performing at any given point in time on the network. Using the included charts, you can identify traffic flow problems visually. This is much easier than having to interpret the numbers in a column of traffic flow data.

User Communities Analysis

User community analysis is the process of identifying various groupings of users and their impact on network performance. The way users are grouped affects issues related to port density and traffic flow, which, in turn, influences the selection of network switches. Port density is explained later in this chapter.

In a typical office building, end users are grouped according to their job function, because they require similar access to resources and applications. You may find the Human Resource (HR) department located on one floor of an office building, while Finance is located on another floor. Each department has a different number of users and application needs, and requires access to different data resources available through the network. For example, when selecting switches for the wiring closets of the HR and Finance departments, you would choose a switch that had enough ports to meet the department needs and was powerful enough to accommodate the traffic requirements for all the devices on that floor. Additionally, a good network design plan factors in the growth of each department to ensure that there are enough open switch ports that can utilized before the next planned upgrade to the network.

As shown in the figure, the HR department requires 20 workstations for its 20 users. That translates to 20 switch ports needed to connect the workstations to the network. If you were to select an appropriate access layer switch to accommodate the HR department, you would probably choose a 24 port switch, which has enough ports to accommodate the 20 workstations and the uplinks to the distribution layer switches.

Future Growth
But this plan does not account for future growth. Consider what will happen if the HR department grows by five employees. A solid network plan includes the rate of personnel growth over the past five years to be able to anticipate the future growth. With that in mind, you would want to purchase a switch that can accommodate more than 24 ports, such as stackable or modular switches that can scale.

As well as looking at the number of devices on a given switch in a network, you should investigate the network traffic generated by end-user applications. Some user communities use applications that generate a lot of network traffic, while other user communities do not. By measuring the network traffic generated for all applications in use by different user communities, and determining the location of the data source, you can identify the effect of adding more users to that community.

A workgroup-sized user community in a small business is supported by a couple of switches and typically connected to the same switch as the server. In medium-sized businesses or enterprises, user communities are supported by many switches. The resources that medium-sized business or enterprise user communities need could be located in geographically separate areas. Consequently, the location of the user communities influences where data stores and server farms are located.



If the Finance users are using a network-intensive application that exchanges data with a specific server on the network, it may make sense to locate the Finance user community close to that server. By locating users close to their servers and data stores, you can reduce the network diameter for their communications, thereby reducing the impact of their traffic across the rest of the network.

One complication of analyzing application usage by user communities is that usage is not always bound by department or physical location. You may have to analyze the impact of the application across many network switches to determine its overall impact.

what is converged network

Small and medium-sized businesses are embracing the idea of running voice and video services on their data networks. Let us look at how voice and video over IP (VoIP) affect a hierarchical network.

Legacy Equipment

Convergence is the process of combining voice and video communications on a data network. Converged networks have existed for a while now, but were only feasible in large enterprise organizations because of the network infrastructure requirements and complex management that was involved to make them work seamlessly. There were high network costs associated with convergence because more expensive switch hardware was required to support the additional bandwidth requirements. Converged networks also required extensive management in relation to Quality of Service (QoS), because voice and video data traffic needed to be classified and prioritized on the network. Few individuals had the expertise in voice, video, and data networks to make convergence feasible and functional. In addition, legacy equipment hinders the process. The figure shows a legacy telephone company switch. Most telephone companies today have made the transition to digital-based switches. However, there are many offices that still use analog phones, so they still have existing analog telephone wiring closets. Because analog phones have not yet been replaced, you will also see equipment that has to support both legacy PBX telephone systems and IP-based phones. This sort of equipment will slowly be migrated to modern IP-based phone switches.

Advanced Technology

Converging voice, video, and data networks has become more popular recently in the small to medium-sized business market because of advancements in technology. Convergence is now easier to implement and manage, and less expensive to purchase. The figure shows a high-end VoIP phone and switch combination suitable for a medium-sized business of 250-400 employees. The figure also shows a Cisco Catalyst Express 500 switch and a Cisco 7906G phone suitable for small to medium-sized businesses. This VoIP technology used to be affordable only to enterprises and governments.

Moving to a converged network can be a difficult decision if the business already invested in separate voice, video, and data networks. It is difficult to abandon an investment that still works, but there are several advantages to converging voice, video, and data on a single network infrastructure.

One benefit of a converged network is that there is just one network to manage. With separate voice, video, and data networks, changes to the network have to be coordinated across networks. There are also additional costs resulting from using three sets of network cabling. Using a single network means you just have to manage one wired infrastructure.

Another benefit is lower implementation and management costs. It is less expensive to implement a single network infrastructure than three distinct network infrastructures. Managing a single network is also less expensive. Traditionally, if a business has a separate voice and data network, they have one group of people managing the voice network and another group managing the data network. With a converged network, you have one group managing both the voice and data networks.



New Options

Converged networks give you options that had not existed previously. You can now tie voice and video communications directly into an employee's personal computer system, as shown in the figure. There is no need for an expensive handset phone or videoconferencing equipment. You can accomplish the same function using special software integrated with a personal computer. Softphones, such as the Cisco IP Communicator, offer a lot of flexibility for businesses. The person in the top left of the figure is using a softphone on the computer. When software is used in place of a physical phone, a business can quickly convert to converged networks, because there is no capital expense in purchasing IP phones and the switches needed to power the phones. With the addition of inexpensive webcams, videoconferencing can be added to a softphone. These are just a few examples provided by a broader communications solution portfolio that redefine business processes today.

Separate Voice, Video and Data Networks

As you see in the figure, a voice network contains isolated phone lines running to a PBX switch to allow phone connectivity to the Public Switched Telephone Network (PSTN). When a new phone is added, a new line has to be run back to the PBX. The PBX switch is typically located in a Telco wiring closet, separate from the data and video wiring closets. The wiring closets are usually separated because different support personnel require access to each system. However, using a properly designed hierarchical network, and implementing QoS policies that prioritize the audio data, voice data can be converged onto an existing data network with little to no impact on audio quality.

In this figure, videoconferencing equipment is wired separately from the voice and data networks. Videoconferencing data can consume significant bandwidth on a network. As a result, video networks were maintained separately to allow the videoconferencing equipment to operate at full speed without competing for bandwidth with voice and data streams. Using a properly designed hierarchical network, and implementing QoS policies that prioritize the video data, video can be converged onto an existing data network with little to no impact on video quality.

The data network interconnects the workstations and servers on a network to facilitate resource sharing. Data networks can consume significant data bandwidth, which is why voice, video, and data networks were kept separated for such a long time. Now that properly designed hierarchical networks can accommodate the bandwidth requirements of voice, video, and data communications at the same time, it makes sense to converge them all onto a single hierarchical network.

Basic VTP Configuration

Learning Objectives

• Perform basic switch configurations

• Configure the Ethernet interfaces on the host PCs

• Configure VTP and security on the switches

Configuration Switch 1
Switch>enable
Switch#configure terminal
Switch(config)#hostname S1
S1(config)#enable secret class
S1(config)#no ip domain-lookup
S1(config)#line console 0
S1(config-line)#password cisco
S1(config-line)#login
S1(config-line)#line vty 0 15
S1(config-line)#password cisco
S1(config-line)#login
S1(config-line)#end
S1#copy running-config startup-config
S1(config)#vtp mode server
S1(config)#vtp domain Lab4
S1(config)#vtp password cisco
S1(config)#end
S1(config)#interface fa0/1
S1(config-if)#switchport mode trunk
S1(config-if)#switchport trunk native vlan 99
S1(config-if)#no shutdown
S1(config-if)#interface fa0/2
S1(config-if)#switchport mode trunk
S1(config-if)#switchport trunk native vlan 99
S1(config-if)#no shutdown
S1(config-if)#end
S1(config)#vlan 99
S1(config-vlan)#name management
S1(config-vlan)#exit
S1(config)#vlan 10
S1(config-vlan)#name faculty/staff
S1(config-vlan)#exit
S1(config)#vlan 20
S1(config-vlan)#name students
S1(config-vlan)#exit
S1(config)#vlan 30
S1(config-vlan)#name guest
S1(config-vlan)#exit
S1(config)#interface vlan 99
S1(config-if)#ip address 172.17.99.11 255.255.255.0
S1(config-if)#no shutdown

Configuration Switch 2
Switch>enable
Switch#configure terminal
Switch(config)#hostname S2
S2(config)#enable secret class
S2(config)#no ip domain-lookup
S2(config)#line console 0
S2(config-line)#password cisco
S2(config-line)#login
S2(config-line)#line vty 0 15
S2(config-line)#password cisco
S2(config-line)#login
S2(config-line)#end
S2#copy running-config startup-config
S2(config)#interface fa0/6
S2(config-if)#switchport mode access
S2(config-if)#no shutdown
S2(config-if)#interface fa0/11
S2(config-if)#switchport mode access
S2(config-if)#no shutdown
S2(config-if)#interface fa0/18
S2(config-if)#switchport mode access
S2(config-if)#no shutdown
S2(config)#vtp mode client
S2(config)#vtp domain Lab4
S2(config)#vtp password cisco
S2(config)#end
S2(config)#interface fa0/1
S2(config-if)#switchport mode trunk
S2(config-if)#switchport trunk native vlan 99
S2(config-if)#no shutdown
S2(config-if)#end
S2(config)#interface fa0/6
S2(config-if)#switchport port-security
S2(config-if)#switchport port-security maximum 1
S2(config-if)#switchport port-security mac-address sticky
S2(config-if)#interface fa0/11
S2(config-if)#switchport port-security
S2(config-if)#switchport port-security maximum 1
S2(config-if)#switchport port-security mac-address sticky
S2(config-if)#interface fa0/18
S2(config-if)#switchport port-security
S2(config-if)#switchport port-security maximum 1
S2(config-if)#switchport port-security mac-address sticky
S2(config-if)#end
S2(config)#interface vlan 99
S2(config-if)#ip address 172.17.99.12 255.255.255.0
S2(config-if)#no shutdown

Configuration Switch 3
Switch>enable
Switch#configure terminal
Switch(config)#hostname S3
S3(config)#enable secret class
S3(config)#no ip domain-lookup
S3(config)#line console 0
S3(config-line)#password cisco
S3(config-line)#login
S3(config-line)#line vty 0 15
S3(config-line)#password cisco
S3(config-line)#login
S3(config-line)#end
S3#copy running-config startup-config
S3(config)#interface fa0/6
S3(config-if)#switchport mode access
S3(config-if)#no shutdown
S3(config-if)#interface fa0/11
S3(config-if)#switchport mode access
S3(config-if)#no shutdown
S3(config-if)#interface fa0/18
S3(config-if)#switchport mode access
S3(config-if)#no shutdown
S3(config)#vtp mode transparent
S3(config)#vtp domain Lab4
S3(config)#vtp password cisco
S3(config)#end
S3(config)#interface fa0/2
S3(config-if)#switchport mode trunk
S3(config-if)#switchport trunk native vlan 99
S3(config-if)#no shutdown
S3(config-if)#end
S3(config)#interface fa0/6
S3(config-if)#switchport port-security
S3(config-if)#switchport port-security maximum 1
S3(config-if)#switchport port-security mac-address sticky
S3(config-if)#interface fa0/11
S3(config-if)#switchport port-security
S3(config-if)#switchport port-security maximum 1
S3(config-if)#switchport port-security mac-address sticky
S3(config-if)#interface fa0/18
S3(config-if)#switchport port-security
S3(config-if)#switchport port-security maximum 1
S3(config-if)#switchport port-security mac-address sticky
S3(config-if)#end
S3(config)#vlan 99
S3(config-vlan)#name management
S3(config-vlan)#exit
S3(config)#vlan 10
S3(config-vlan)#name faculty/staff
S3(config-vlan)#exit
S3(config)#vlan 20
S3(config-vlan)#name students
S3(config-vlan)#exit
S3(config)#vlan 30
S3(config-vlan)#name guest
S3(config-vlan)#exit
S3(config)#interface vlan 99
S3(config-if)#ip address 172.17.99.13 255.255.255.0
S3(config-if)#no shutdown
S3(config)#interface fa0/6
S3(config-if-range)#switchport access vlan 30
S3(config-if-range)#interface fa0/11
S3(config-if-range)#switchport access vlan 10
S3(config-if-range)#interface fa0/18
S3(config-if-range)#switchport access vlan 20
S3(config-if-range)#end
S3#copy running-config startup-config

Configuring STP

Task 1: Examine the STP Default State
Step 1. Examine link lights.
When STP is fully converged, the following conditions exist:
All PCs have green link lights on the switched ports.
Access layer switches have one forwarding uplink (green) to a distribution layer switch and a blocking uplink (amber) to a core layer switch.
Distribution layer switches have one forwarding uplink (green) to a core layer switch and a blocking uplink (amber) to another core layer switch.
Step 2. Switch to Simulation mode.
Step 3. Determine the root bridge.
Click Capture/Forward. Without looking at BPDU detail, MAC addresses, or the show spanning-tree command, can you tell which switch is the root bridge?
Can you think of a reason why this switch is not a good choice as root?
Task 2: Configure the Root Bridge
Step 1. Configure the root bridge.
One of the core switches should be root, and the other should be the backup root. Switch to Realtime mode and configure C1 with a priority of 4096.
Step 2. Switch between Realtime and Simulation modes.
Switch between Realtime mode and Simulation mode several times until all ports on C1 are green.
Step 3. Switch to Simulation mode.
Step 4. Make sure C1 is the root bridge.
Click Capture/Forward several times to watch configuration BPDUs. C1 should be initiating the propagation of BPDUs.
Step 5. Check results.
Your completion percentage should be 17%. If not, click Check Results to see which required components are not yet completed.
Task 3: Configure the Backup Root Bridge
Step 1. Configure the backup root bridge.
The other core switch serves as a backup root bridge. Switch to Realtime mode and configure C2 with a priority of 8192.
Step 2. Switch between Realtime and Simulation modes.
Switch between Realtime mode and Simulation mode several times until all ports on C2 are green.
Step 3. Examine links attached to C2.
What is unique about the C2 links to the distribution layer switches that you do not see with C1 links?
Step 4. Check results.
Your completion percentage should be 33%. If not, click Check Results to see which required components are not yet completed.
Task 4: Finalize STP Configuration
Best practice is to never have an access layer switch become root. You could ensure this by configuring all access layer switches with a priority higher than the default. However, because there are fewer distribution switches, it is more efficient to configure these switches with a slightly higher priority than the backup root switch.
Step 1. Configure distribution switches.
Configure D1, D2, D3, and D4 with a priority of 12288.

Switched LAN Architecture

Access Layer

The access layer interfaces with end devices, such as PCs, printers, and IP phones, to provide access to the rest of the network. The access layer can include routers, switches, bridges, hubs, and wireless access points. The main purpose of the access layer is to provide a means of connecting devices to the network and controlling which devices are allowed to communicate on the network.

Distribution Layer

The distribution layer aggregates the data received from the access layer switches before it is transmitted to the core layer for routing to its final destination. The distribution layer controls the flow of network traffic using policies and delineates broadcast domains by performing routing functions between virtual LANs (VLANs) defined at the access layer. VLANs allow you to segment the traffic on a switch into separate subnetworks. For example, in a university you might separate traffic according to faculty, students, and guests. Distribution layer switches are typically high-performance devices that have high availability and redundancy to ensure reliability. You will learn more about VLANs, broadcast domains, and inter-VLAN routing later in this course.

Core Layer

The core layer of the hierarchical design is the high-speed backbone of the internetwork. The core layer is critical for interconnectivity between distribution layer devices, so it is important for the core to be highly available and redundant. The core area can also connect to Internet resources. The core aggregates the traffic from all the distribution layer devices, so it must be capable of forwarding large amounts of data quickly.

A Hierarchical Network in a Medium-Sized Business
Let us look at the hierarchical network model applied to a business. In the figure, the access, distribution, and core layers are separated into a well-defined hierarchy. This logical representation makes it easy to see which switches perform which function. It is much harder to see these hierarchical layers when the network is installed in a business.

The figure shows two floors of a building. The user computers and network devices that need network access are on one floor. The resources, such as e-mail servers and database servers, are located on another floor. To ensure that each floor has access to the network, access layer and distribution switches are installed in the wiring closets of each floor and connected to each of the devices needing network access. The figure shows a small rack of switches. The access layer switch and distribution layer switch are stacked one on top of each other in the wiring closet.

Although the core and other distribution layer switches are not shown, you can see how the physical layout of a network differs from the logical layout of a network.

Benefits of a Hierarchical Network

There are many benefits associated with hierarchical network designs.

Scalability

Hierarchical networks scale very well. The modularity of the design allows you to replicate design elements as the network grows. Because each instance of the module is consistent, expansion is easy to plan and implement. For example, if your design model consists of two distribution layer switches for every 10 access layer switches, you can continue to add access layer switches until you have 10 access layer switches cross-connected to the two distribution layer switches before you need to add additional distribution layer switches to the network topology. Also, as you add more distribution layer switches to accommodate the load from the access layer switches, you can add additional core layer switches to handle the additional load on the core.

Redundancy

As a network grows, availability becomes more important. You can dramatically increase availability through easy redundant implementations with hierarchical networks. Access layer switches are connected to two different distribution layer switches to ensure path redundancy. If one of the distribution layer switches fails, the access layer switch can switch to the other distribution layer switch. Additionally, If one of the distribution layer switches fails, the access layer switch can switch to the other distribution layer switch. Additionally, distribution layer switches are connected to two or more core layer switches to ensure path availability if a core switch fails. The only layer where redundancy is limited is at the access layer. Typically, end node devices, such as PCs, printers, and IP phones, do not have the ability to connect to multiple access layer switches for redundancy. If an access layer switch fails, just the devices connected to that one switch would be affected by the outage. The rest of the network would continue to function unaffected.

Performance

Communication performance is enhanced by avoiding the transmission of data through low-performing, intermediary switches. Data is sent through aggregated switch port links from the access layer to the distribution layer at near wire speed in most cases. The distribution layer then uses its high performance switching capabilities to forward the traffic up to the core, where it is routed to its final destination. Because the core and distribution layers perform their operations at very high speeds, there is no contention for network bandwidth. As a result, properly designed hierarchical networks can achieve near wire speed between all devices.

Security

Security is improved and easier to manage. Access layer switches can be configured with various port security options that provide control over which devices are allowed to connect to the network. You also have the flexibility to use more advanced security policies at the distribution layer. You may apply access control policies that define which communication protocols are deployed on your network and where they are permitted to go. For example, if you want to limit the use of HTTP to a specific user community connected at the access layer, you could apply a policy that blocks HTTP traffic at the distribution layer. Restricting traffic based on higher layer protocols, such as IP and HTTP, requires that your switches are able to process policies at that layer. Some access layer switches support Layer 3 functionality, but it is usually the job of the distribution layer switches to process Layer 3 data, because they can process it much more efficiently.

Manageability

Manageability is relatively simple on a hierarchical network. Each layer of the hierarchical design performs specific functions that are consistent throughout that layer. Therefore, if you need to change the functionality of an access layer switch, you could repeat that change across all access layer switches in the network because they presumably perform the same functions at their layer. Deployment of new switches is also simplified because switch configurations can be copied between devices with very few modifications. Consistency between the switches at each layer allows for rapid recovery and simplified troubleshooting. In some special situations, there could be configuration inconsistencies between devices, so you should ensure that configurations are well documented so that you can compare them before deployment.

Maintainability

Because hierarchical networks are modular in nature and scale very easily, they are easy to maintain. With other network topology designs, manageability becomes increasingly complicated as the network grows. Also, in some network design models, there is a finite limit to how large the network can grow before it becomes too complicated and expensive to maintain. In the hierarchical design model, switch functions are defined at each layer, making the selection of the correct switch easier. Adding switches to one layer does not necessarily mean there will not be a bottleneck or other limitation at another layer. For a full mesh network topology to achieve maximum performance, all switches need to be high-performance switches, because each switch needs to be capable of performing all the functions on the network. In the hierarchical model, switch functions are different at each layer. You can save money by using less expensive access layer switches at the lowest layer, and spend more on the distribution and core layer switches to achieve high performance on the network.

Grouping Basic Programming Language

If the source comes from the natural language is the language of construction will be similar to the real meaning.
It will certainly make it easier for programmers to program, especially for those who have not experienced.
Sometimes it can be ambiguous, because sometimes a lot of natural language that has many meanings. Example: SQL.

If the source comes from the language of mathematics would be very logical, mathematical, and full of functions and formulas. Example: MATLAB, Scilab, MathCad
If the source comes from an existing programming language, so programmers will be easier to use, especially when the language is formed comes from the already very famous.

Information Input and Output

INPUT DEVICES

• Input devices translate our
  data and communications into
  a form that the computer can
  understand
• The computer processes the
  data
• Output devices translate the
  data back into a form we can
  understand

THE KEYBOARD
Two types of keyboards
- Alphanumeric

• Typical keyboard has 101 keys
• 12 function keys
• Special-function keys
• Cursor-control key

- Special Function

• Designed for specific application
• Example: cash register

POINT-AND-DRAW DEVICES

• GUI lets you point and click
• With a mouse you can draw,
  drag and drop, click, and
  double-click
• A mouse can have one or two
  buttons, and some have a
  wheel for scrolling

SCANNERS

• Scanners read and
  interpret information on
  printed matter
• The information is
  converted to a format for
  storage

OCR AND BAR CODE SCANNERS

• Optical character
  recognition (OCR)
  Reads coded information
  and text
  Types
  - Contact and Laser
  - Handheld
  - Label
  Document
  

Flag Register

Carry flag is generally composed of nine pieces

• Flow Over Flag (OF): Value 1 if there is overflow (OV) and set to 0 (NV).
  

• Sign Flag (SF): Distinguishing numbers marked. Positive numbers (PL) or a negative number (NG).
• Zero Flag (ZF): Value 0, if the result is worth one operation.
• Carry Flag (CF): Value 1 in case (borrow) on the subtraction operation or (carry) on the addition operation.
• Parity Flag (PF): Value 1 if an even
• Direction Flag: Used for string operations
• Interupst Enable Flag (IF): If the value 0, meaning no interruption of running.
• Trap Flag (TF): Used for debugging.
• Auxiliary Flag (AF): Used in BCD operation
  

B.Mnemonic	B.Mesin	Isi Register
LDA,C7H	3ec7	2105 5.A
ADD A,B	5D	2102 A.5
LD L,A	6f	2103 5.A
LD A,00H	3e20 00	2106 A.5
ADC A 00H	c620 00	2109 5.A
LD H,A	67	2110 A.5
RST 08	cf	2111 5.A

after entry into Z80 machine language, a road with a RESET command-MEM-RUN from step 0 to 7 to check the contents of registers

lets trY
GOOD LUCK

Definition Multimedia

The term multimedia is the combination of multiple words and the media. Multi word
means much or more than one, while the media has meant a means or tool for
communicate. So Multimedia means a system consisting of hardware, software
and other tools to support information processing. 1
In the electronics industry, Multimedia is a combination of computer and video
(Rosch, 1996) or multimedia in general is a combination of three elements, namely voice,
images, and text (McCornick, 1996) or Multimedia is a combination of the most
least two media inputs or from data, these media can be an audio (voice, music), animation,
video, text, graphics and images (Turban et al, 2002) or Multimedia is a tool that
can create dynamic and interactive presentation that combines text,
graphics, animation, audio, images and video (Robin and Linda, 2001)

A. Text (Text)
Text is one of the elements of multimedia which is helpful in
clarify information for consumers. In this text there are various kinds of
character is provided and its user depends on the ads or theme
appointed.

B. Picture (Image)
Pictures or graphics is an important part in the multimedia world.
Because a picture can describe a thousand words. With a
pictures, messages can be expressed with more beautiful and easier.

C. Sound (Audio)
Several years ago, PC users are quite satisfied with the PC speakers
that only a certain tone at a time. In technology
multimedia, voice high enough to have a role when we consider the vision
The main multimedia information that is exploiting all the human senses, especially
eyes and ears.

D. Video
A composite video images to be read sequentially dead
in a time with a certain speed. These images are combined
is called the frame and the speed of reading is called a framed picture
rate, with units of fps (frames per second). Since playing in the speed
high then created the illusion of smooth motion, the greater the value of the frame rate
the more subtle movements of the displayed

Personality

one's personality or character that can be identified with the personality test. it all starts from the environment and education of parents. everyone has a different personality to another. It consists of four personality types of people sanguinis, pleghmantis, korelis, and melancholy

want to test your personality?
please download this file Personality

Introduction to HTML

HTML or HyperText Markup Language is one of the format used in the production of documents and applications that are running are at the web. HTML is a pure text file that can be created with any text editor. This document is known as a web page, the HTML document is a document that is presented in a web browser. There are two ways of writing an HTML document which will form the a browser page. The first is to use HTML editor or web editor, and the second uses ordinary text editor like notepad.
There is now a lot of application packages that can be used to create web pages in a WYSIWYG (What You See Is What You Get) such as FrontPage, Dreamweaver, etc, you still have to master HTML tags that are used primarily to create applications on the Internet because they inevitably you will be working in text mode editor if you would insert any HTML script.


HTML and HTML document naming
In naming a document that will be displayed on web browser use the name must end with extension (. Html) or (. Htm). Extension of the HTML document was originally three characters, is to accommodate the naming system in DOS. In a document given name is case sensitive so that documents with names will be different from the document a.html A.html.
Prior to further study the HTML tags is a good idea first to see the color code that is often used in writing HTML tags. HTML color settings are at using a combination mode RGB (red, green, blue) in which each color is displayed in two digit hexadecimal values (0,1,2, ... F). Every part of the two digit code indicates the number of intensity of red color combination , green and blue. For example in 2000 the first two digits means no red color and so on.

Color Hexadecimal
White # FFFFFF
Black # 000 000
Red # FF0000
Green # 00FF00
Blue # 0000FF
Magenta # FF00FF

HTML Tag Element and Definition
An HTML document prepared by some element, or better known as the basic components. Elements can be either pure text, or instead of text, or both. Elements or parts eg head, body, paragraphs, lists etc..
To mark an element in an HTML document used tags. ,lebih besar), contoh

, tag pada umumnya berpasangan (misalnya

dengan

), tanda" onmouseover="this.style.backgroundColor='#ebeff9'" onmouseout="this.style.backgroundColor='#fff'">HTML tags consist of a left angle brackets (<, smaller), name tags, the right angle brackets (>, greater),

example, tags are generally in pairs (eg

with ), mark / on the tag pair gives a sign that the tag is the final barrier element that was opened by the initial tag.
The name of the element indicated by the name of the tags. An element usually marked with a tag partner, although there is some element name is marked with a tag without having pairs. Among them are:

• " onmouseover="this.style.backgroundColor='#ebeff9'" onmouseout="this.style.backgroundColor='#fff'">Paragraph tags

• " onmouseover="this.style.backgroundColor='#ebeff9'" onmouseout="this.style.backgroundColor='#fff'">Replace the line - the line break tags
  

• " onmouseover="this.style.backgroundColor='#ebeff9'" onmouseout="this.style.backgroundColor='#fff'">Flat line - a horizontal rule tags

  ---

• " onmouseover="this.style.backgroundColor='#ebeff9'" onmouseout="this.style.backgroundColor='#fff'">List item tags
• 
  

... selain itu dalam penamaan tag tidak menganut case sensitive." onmouseover="this.style.backgroundColor='#ebeff9'" onmouseout="this.style.backgroundColor='#fff'">So in general the writing of a tag is name> tag> ... other than that in the naming of the tags did not subscribe to case sensitive.
In making the basic elements of an HTML document that must be owned is the html tag, head tag and tag body. Head element contains information about the document, while the body element contains the text and / or other elements. Or more details as follows:

" onmouseover="this.style.backgroundColor='#ebeff9'" onmouseout="this.style.backgroundColor='#fff'">
" onmouseover="this.style.backgroundColor='#ebeff9'" onmouseout="this.style.backgroundColor='#fff'">
Document information .... ....
" onmouseover="this.style.backgroundColor='#ebeff9'" onmouseout="this.style.backgroundColor='#fff'">
" onmouseover="this.style.backgroundColor='#ebeff9'" onmouseout="this.style.backgroundColor='#fff'">
That the information in the show ....
on the browser page .....
" onmouseover="this.style.backgroundColor='#ebeff9'" onmouseout="this.style.backgroundColor='#fff'">
" onmouseover="this.style.backgroundColor='#ebeff9'" onmouseout="this.style.backgroundColor='#fff'">


Use Tags and Tag Attributes
In making the writing element of an HTML document that begins and ends mark the HTML tags, have a writing requirement, namely:

• )" onmouseover="this.style.backgroundColor='#ebeff9'" onmouseout="this.style.backgroundColor='#fff'">HTML tags are enclosed in angle brackets with two characters ()

• ...)" onmouseover="this.style.backgroundColor='#ebeff9'" onmouseout="this.style.backgroundColor='#fff'">HTML tags are normally always in pairs eg (Addons ...)
• ...)" onmouseover="this.style.backgroundColor='#ebeff9'" onmouseout="this.style.backgroundColor='#fff'">Tag pertama dalam suatu pasangan adalah tag awal, dan tag yang kedua merupakan tag akhir...)" onmouseover="this.style.backgroundColor='#ebeff9'" onmouseout="this.style.backgroundColor='#fff'">
• ...)" onmouseover="this.style.backgroundColor='#ebeff9'" onmouseout="this.style.backgroundColor='#fff'">Tag html tidak ‘case sensitive’. sama dengan
  ...)" onmouseover="this.style.backgroundColor='#ebeff9'" onmouseout="this.style.backgroundColor='#fff'">
• ...)" onmouseover="this.style.backgroundColor='#ebeff9'" onmouseout="this.style.backgroundColor='#fff'">Jika dalam suatu tag ada tag lagi, maka penulisan tag akhir tidak boleh bersilang harus berurutan. Misalnya ..Tebal dan Miring..