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CCNA Basic Switching and Switch Configuration
 

CCNA Basic Switching and Switch Configuration

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    CCNA Basic Switching and Switch Configuration CCNA Basic Switching and Switch Configuration Presentation Transcript

    • CCNA Guide to Cisco Networking Fundamentals Chapter 12 Basic Switching and Switch Configuration
    • Objectives
      • Explain the technology and media access control method for Ethernet networks
      • Explain network segmentation and basic traffic management concepts
      • Explain basic switching concepts and the operation of Cisco switches
      • Perform and verify switch configuration tasks
      • Implement basic switch security
      CCNA Guide to Cisco Networking Fundamentals
    • Ethernet Operations
      • Ethernet
        • A network access method (or media access method ) originated by the University of Hawaii, later adopted by Xerox Corporation
        • And standardized as IEEE 802.3 in the early 1980s
      • Ethernet is:
        • Most pervasive network access method in use
        • Most commonly implemented media access method in new LANs
      CCNA Guide to Cisco Networking Fundamentals
    • CSMA/CD
      • Carrier Sense Multiple Access with Collision Detection (CSMA/CD)
        • Ethernet contention method
      • Any station connected to a network can transmit anytime a transmission is not present on the wire
      • Interframe gap , or interpacket gap (IPG)
        • After each transmitted signal, each station must wait a minimum of 9.6 microseconds before transmitting another packet
      CCNA Guide to Cisco Networking Fundamentals
    • CSMA/CD (continued)
      • Collisions
        • Two stations could listen to the wire simultaneously and not sense a carrier signal
        • Both stations might begin to transmit their data simultaneously
        • Once a collision is detected, the first station to detect the collision transmits a 32-bit jam signal
          • Tells all other stations not to transmit for a brief period
        • The two stations that caused the collision use an algorithm to enter a backoff period
      CCNA Guide to Cisco Networking Fundamentals
    • CSMA/CD (continued)
      • Collision domain
        • The physical area in which a packet collision might occur
        • Routers, switches, bridges, and gateways segment networks
          • And thus create separate collision domains
        • The 32-bit jam signal that is transmitted when the collision is discovered prevents all stations on that collision domain from transmitting
      CCNA Guide to Cisco Networking Fundamentals
    • CSMA/CD (continued)
      • Broadcasts
        • Stations on a network broadcast packets to other stations to make their presence known on the network
          • And to carry out normal network tasks
        • When a segment has too much broadcast traffic:
          • Utilization increases
          • Network performance in general suffers
        • Simple ways to reduce broadcast traffic:
          • Reduce the number of services on your network
          • Limit the number of protocols in use on your network
      CCNA Guide to Cisco Networking Fundamentals
    • CSMA/CD (continued)
      • Broadcast storm
        • A sudden rush of network transmissions that causes all other network communications to slow down
          • Due to the volume of data competing for access to the same bandwidth on the communications medium
      • One of the most common causes of broadcast storms is a network loop
      CCNA Guide to Cisco Networking Fundamentals
    • Latency
      • Latency , or propagation delay
        • The length of time that is required to forward, send, or otherwise propagate a data frame
        • Latency differs depending on the resistance offered by the transmission medium, the number of nodes
          • And in the case of a connectivity device, the amount of processing that must be done on the packet
      • Transmission time
        • The amount of time it takes for a packet to be sent from one device to another
      CCNA Guide to Cisco Networking Fundamentals
    • Latency (continued) CCNA Guide to Cisco Networking Fundamentals
    • Latency (continued)
      • Bit time
        • Refers to the amount of time required to transmit one data bit on a network
      • Slot time (512 bit times)
        • An important specification that limits the physical size of each Ethernet collision domain
        • Specifies that all collisions should be detected from anywhere in a network in less time than is required to place a 64-byte frame on the network
      CCNA Guide to Cisco Networking Fundamentals
    • Ethernet Errors
      • Frame size errors
        • Short frame or runt
        • Long frame or giant
        • Jabber
      • Frame check sequence (FCS) error
        • Indicates that bits of a frame were corrupted during transmission
        • Can be caused by any of the previously listed errors
      CCNA Guide to Cisco Networking Fundamentals
    • Ethernet Errors (continued)
      • Collision errors
        • Reducing the number of devices per collision domain will usually solve the problem
          • You can do this by segmenting your network with a router, a bridge, or a switch
        • Late collision
          • Occurs when two stations transmit more than 64 bytes of data frames before detecting a collision
      CCNA Guide to Cisco Networking Fundamentals
    • Ethernet Errors (continued)
      • Fast Ethernet
        • Uses the same CSMA/CD as common 10BaseT Ethernet
        • Provides ten times the data transmission rate—100 Mbps
        • Defined under the IEEE 802.3u standard
      • Implementations
        • 100Base-TX
        • 100Base-T4
        • 100Base-FX
      CCNA Guide to Cisco Networking Fundamentals
    • Gigabit Ethernet
      • Recent advances in technology have allowed us to reach even higher speeds than those of Fast Ethernet
      • Gigabit Ethernet implementations
        • 1000Base-TX (802.3ab)
        • 1000Base-SX (802.3z)
        • 1000Base-LX (802.3z)
        • 1000Base-CX (802.3z)
      CCNA Guide to Cisco Networking Fundamentals
    • Half- and Full-Duplex Communications
      • Half-duplex communications
        • Devices can send and receive signals, but not at the same time
      • Full-duplex (or duplex ) communications
        • Devices can send and receive signals simultaneously
      • Ethernet networks can use equipment that supports half- and full-duplex communications
      CCNA Guide to Cisco Networking Fundamentals
    • CCNA Guide to Cisco Networking Fundamentals
    • Half- and Full-Duplex Communications (continued)
      • Benefits of using full-duplex:
        • Time is not wasted retransmitting frames because collisions do not occur
        • The full bandwidth is available in both directions because the send and receive functions are separate
        • Stations do not have to wait until other stations complete their transmissions because only one transmitter is used for each twisted pair
      CCNA Guide to Cisco Networking Fundamentals
    • Half- and Full-Duplex Communications (continued)
      • On a Cisco Catalyst 2950 switch, you can set the duplex capabilities port-by-port
      • The four different duplex options are:
        • Auto
        • Full
        • Full-flow control
        • Half
      CCNA Guide to Cisco Networking Fundamentals
    • A Review of LAN Segmentation
      • You can improve the performance of your Ethernet network
        • By reducing the number of stations per collision domain
      • Typically, network administrators implement bridges, switches, or routers to segment the network and divide the collision domains
      CCNA Guide to Cisco Networking Fundamentals
    • Segmenting with Bridges
      • Bridge
        • Segments a network by filtering traffic at the Data Link layer
        • Divides a network into two or more segments
          • Only forwards a frame from one segment to another if the frame is a broadcast or has the MAC address of a station on a different segment
      • Bridges learn MAC addresses by reading the source MAC addresses from frames
        • As the frames are passed across the bridge
      CCNA Guide to Cisco Networking Fundamentals
    • Segmenting with Bridges (continued)
      • Bridging table
        • Maps the MAC addresses on each segment to the corresponding port on the bridge to which each segment is connected
      • Bridges increase latency, but because they effectively divide the collision domain
        • This does not affect slot time
      CCNA Guide to Cisco Networking Fundamentals
    • Segmenting with Bridges (continued)
      • Remember these points:
        • Bridges reduce collisions on the LAN and filter traffic based on MAC addresses
        • A bridge does not reduce broadcast or multicast traffic
        • A bridge can extend the useful distance of the Ethernet LAN
        • The bandwidth for the new individual segments is increased
        • Bridges can be used to limit traffic for security purposes
      CCNA Guide to Cisco Networking Fundamentals
    • Segmenting with Routers
      • Router
        • Operates at layer 3 of the OSI reference model
        • Interprets the Network layer protocol and makes forwarding decisions based on the layer 3 address
      • Routers typically do not propagate broadcast traffic
        • Thus, they reduce network traffic even more than bridges do
      • Routers maintain routing tables that include the Network layer addresses of different segments
      CCNA Guide to Cisco Networking Fundamentals
    • Segmenting with Routers (continued)
      • When you segment a LAN with routers, they will:
        • Decrease collisions by filtering traffic
        • Reduce broadcast and multicast traffic by blocking or selectively filtering packets
        • Support multiple paths and routes between them
        • Provide increased bandwidth for the newly created segments
        • Increase security by preventing packets between hosts on one side of the router from propagating to the other side of the router
      CCNA Guide to Cisco Networking Fundamentals
    • Segmenting with Routers (continued)
      • When you segment a LAN with routers, they will: (continued)
        • Increase the effective distance of the network by creating new collision domains
        • Provide layer 3 routing, packet fragmentation and reassembly, and traffic flow control
        • Provide communications between different technologies, such as Ethernet and Token Ring or Ethernet and Frame Relay
        • Have a higher latency than bridges, because routers have more to process; faster processors in the router can reduce some of this latency
      CCNA Guide to Cisco Networking Fundamentals
    • LAN Switching
      • Switches
        • Similar to bridges in several ways
      • Using a switch on a LAN has a different effect on the way network traffic is propagated
      CCNA Guide to Cisco Networking Fundamentals
    • Segmentation with Switches
      • Switches are often called multiport bridges
      • Switch typically connects multiple stations individually
        • Thereby segmenting a LAN into multiple collision domains
      • Switches microsegment the network
        • By connecting each port to an individual workstation
      • Switched bandwidth
        • Bandwidth is not shared as long as each workstation connects to its own switch port
      CCNA Guide to Cisco Networking Fundamentals
    • Segmentation with Switches (continued) CCNA Guide to Cisco Networking Fundamentals
    • CCNA Guide to Cisco Networking Fundamentals
    • Segmentation with Switches (continued)
      • Switch latency is typically higher than that of a repeater or hub
        • Faster processors and a variety of switching techniques make switches typically faster than bridges
      • Switches provide the following benefits:
        • Reduction in network traffic and collisions
        • Increase in available bandwidth per station
        • Increase in the effective distance of a LAN by dividing it into multiple collision domains
        • Increased security, because unicast traffic is sent directly to its destination
      CCNA Guide to Cisco Networking Fundamentals
    • Switch Operations
      • A switch learns the hardware address of devices to which it is attached
        • By reading the source address of frames as they are transmitted across the switch
      • The switch then matches the source MAC address with the port from which the frame was sent
        • The MAC-to-switch-port mapping is stored in the switch’s content-addressable memory (CAM)
      • The switch uses a memory buffer to store frames as it determines to which port(s) a frame will be forwarded
      CCNA Guide to Cisco Networking Fundamentals
    • Switch Operations (continued)
      • Types of memory buffering:
        • Port-based memory buffering
        • Shared memory buffering
      • Asymmetric switching
        • Some switches can interconnect network interfaces of different speeds
      • Symmetric switching
        • Switches that require all attached network interface devices to use the same transmit/receive speed
      CCNA Guide to Cisco Networking Fundamentals
    • Switching Methods
      • All switches base frame-forwarding decisions on a frame’s destination MAC address
      • The three main methods for processing and forwarding frames are:
        • Cut-through, store-and-forward, and fragment-free
      • One additional forwarding method, adaptive cut-through forwarding
        • A combination of the cut-through and store-and-forward methods
      CCNA Guide to Cisco Networking Fundamentals
    • Switching Methods (continued) CCNA Guide to Cisco Networking Fundamentals
    • Cut-Through Forwarding
      • Switches that use cut-through forwarding start sending a frame immediately after reading the destination MAC address into their buffers
      • The main benefit of cut-through forwarding is a reduction in latency
      • The drawback is the potential for errors in the frame that the switch would be unable to detect
        • Because the switch only reads a small portion of the frame into its buffer
      CCNA Guide to Cisco Networking Fundamentals
    • Cut-Through Forwarding (continued) CCNA Guide to Cisco Networking Fundamentals
    • Store-and-Forward Forwarding
      • Store-and-forward switches read the entire frame, no matter how large, into their buffers before forwarding
      • Because the switch reads the entire frame, it will not forward frames with errors
      • The store-and-forward method has the highest latency
      CCNA Guide to Cisco Networking Fundamentals
    • Store-and-Forward Forwarding (continued) CCNA Guide to Cisco Networking Fundamentals
    • Fragment-Free Forwarding
      • Fragment-free forwarding represents an effort to provide more error-reducing benefits than cut-through switching
        • While keeping latency lower than does store-and-forward switching
      • A fragment-free switch reads the first 64 bytes of an Ethernet frame
        • And then begins forwarding it to the appropriate port(s)
      CCNA Guide to Cisco Networking Fundamentals
    • Fragment-Free Forwarding (continued) CCNA Guide to Cisco Networking Fundamentals
    • Fragment-Free Forwarding (continued)
      • Adaptive cut-through
        • For the most part, the adaptive cut-through switch will act as a cut-through switch
          • To provide the lowest latency
        • However, if a certain level of errors is detected, the switch will:
          • Change forwarding techniques
          • Act more as a store-and-forward switch
      CCNA Guide to Cisco Networking Fundamentals
    • Switch User Interface
      • Two types of operating systems are in use on Cisco switches: IOS-based and set-based
      • You can connect to a Cisco switch in the same way you connect to a Cisco router
      • The Cisco switch has a console port to which you can connect your laptop or PC
      • Once you power on the switch you will be in the command-line interface
        • You can configure anything from the command line
      CCNA Guide to Cisco Networking Fundamentals
    • Modes and Passwords
      • You cannot actually configure a switch until you get to enable mode
      • To enter enable mode, type enable at the command-line prompt and then press Enter
      • The first step in configuring a switch is to set up a password
      • To start configuration mode, first type configure terminal or config t at the command prompt
      • You can also configure a secret (encrypted) password
      CCNA Guide to Cisco Networking Fundamentals
    • Setting the Host Name
      • The actual task of setting the host name on the Cisco Catalyst switch is identical to setting the host name on a Cisco router
      • To configure this name, you would type:
        • Switch(config)#hostname name
      • Once the host name is set, the prompt will change to reflect the name of the switch
      CCNA Guide to Cisco Networking Fundamentals
    • IP on the Switch
      • By default, Cisco switches are not configured with IP addresses
        • Generally speaking, a switch does not require an IP address
          • Because switches operate mainly on Layer 2
      • You may want to configure an IP address for your switch so that you can manage it over the network
      • Also, you may need to configure an IP address for your switch if you want to implement VLANs on your network
      CCNA Guide to Cisco Networking Fundamentals
    • Configuring Switch Ports
      • To enter interface configuration mode for the first port of a switch named Rm410HL, you would use the following commands:
        • Rm410HL#configure terminal
        • Rm410HL(config)#interface f0/1
        • Rm410HL(config-if)#
      • To view the configuration of a port, use the show command
      CCNA Guide to Cisco Networking Fundamentals
    • Configuring Switch Ports (continued)
      • Configuring the duplex mode
        • You would use the following command to set the duplex mode:
          • Rm410HL#configure terminal
          • Rm410HL(config)#interface f0/24
          • Rm410HL(config-if)#duplex full
      CCNA Guide to Cisco Networking Fundamentals
    • Securing Switch Ports
      • You can choose from several degrees of security on a switch
        • First, you can configure a permanent MAC address for a specific port on your switch
        • Second, you could define a static MAC address entry into your switching table
          • Which maps a restricted communication path between two ports
      • To configure port security, you first must enter the interface configuration mode
      CCNA Guide to Cisco Networking Fundamentals
    • Securing Switch Ports (continued)
      • You can display several options by typing the following command:
        • Rm410HL(config-if)#switchport port-security ?
        • Options include aging , mac-address , maximum , and violation
      • To turn switchport security off, use:
        • Rm410HL(config-if)#no switchport port-security
      • To clear the settings to include erasing the static MAC addresses, use the clear command:
        • Rm410HL(config-if)#clear port-security
      CCNA Guide to Cisco Networking Fundamentals
    • Summary
      • Ethernet (CSMA/CD) is a media access method that was developed in the 1960s
      • Stations on an Ethernet LAN must listen to the network media before transmitting to ensure that no other station is currently transmitting
      • If two stations transmit simultaneously on the same collision domain, a collision will occur
      • The transmitting stations must be able to recognize the collision and ensure that other stations know about it by transmitting a jam signal
      CCNA Guide to Cisco Networking Fundamentals
    • Summary (continued)
      • The delays caused by collisions on a network can seriously affect performance when collisions exceed 5% of the traffic on the collision domain
      • Switches do the most to divide the collision domain and reduce traffic without dividing the broadcast domain
      • A switch microsegments unicast traffic
      • Another way to increase the speed at which a LAN operates is to upgrade from Ethernet to Fast Ethernet
      • Full duplex can also improve Ethernet performance
      CCNA Guide to Cisco Networking Fundamentals
    • Summary (continued)
      • Full duplex allows frames to be sent and received simultaneously
      • As with Fast Ethernet, full-duplex operations are only supported by devices designed for this type of communication
      • The two types of operating systems on Cisco switches are IOS-based and set-based
      • Configuring a switch is similar to configuring a router through the CLI
      • Switches can provide some level of security through the use of port security commands
      CCNA Guide to Cisco Networking Fundamentals