ccna3_ch4.0

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    CCNA3: Switching Basics and Intermediate Routing v3.0

    CISCO NETWORKING ACADEMY PROGRAM

    Switching Concepts

    Introduction to Ethernet/802.3 LANs

    Introduction to LAN SwitchingSwitch Operation

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    CCNA3: Switching Basics and Intermediate Routing v3.0

    CISCO NETWORKING ACADEMY PROGRAM

    Chapter 4 Switching Concepts

    Ethernet Technology Overview Ethernet multi-access

    broadcast technology

    Uses CSMA/CD

    Collisions impact on

    network performance

    Layer 2 devices can

    improve performance

    Media includes CAT5(e),

    fibre, wireless

    Speeds from 10Mbps to

    10,000 Mbps

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    CCNA3: Switching Basics and Intermediate Routing v3.0

    CISCO NETWORKING ACADEMY PROGRAM

    Chapter 4 Switching Concepts

    Network Growth

    Bandwidth needs have increased

    Internet/intranet/email

    Multimedia Increasing use of enterprise servers

    Ethernet has developed to meet challenge

    10Mbps, 100Mbps, 1000Mbps, 10Gbit

    Coaxial, Twisted Pair, Fibre Optic, Wireless

    Repeaters, hubs, bridges, switches, routers

    BUT you must understand the features of all this

    technology to gain best performance in your network

    design!

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    CCNA3: Switching Basics and Intermediate Routing v3.0

    CISCO NETWORKING ACADEMY PROGRAM

    Chapter 4 Switching Concepts

    Hubs Layer 1 devices

    Regenerate, retime,

    amplify signals 1 collision/bandwidthdomain

    Broadcasts propagatedout of every port

    Only 1 device cantransmit at a time

    Only 50-60% bandwidthavailable

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    CCNA3: Switching Basics and Intermediate Routing v3.0

    CISCO NETWORKING ACADEMY PROGRAM

    Chapter 4 Switching Concepts

    Bridges Layer 2 device

    Splits network into 2

    collision/bandwidthdomains

    Broadcasts are forwarded

    Local traffic stays local

    Checks Layer 2 MACaddresses in 802.3 frame

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    CCNA3: Switching Basics and Intermediate Routing v3.0

    CISCO NETWORKING ACADEMY PROGRAM

    Chapter 4 Switching Concepts

    Switches Layer 2 device

    Learns MAC addresses of

    devices attached to each port

    Each switchport is a collision

    domain

    More collision domains BUT

    smaller collision domains

    Broadcasts still sent out ofevery port

    Each switchport has dedicated

    bandwidth

    100% bandwidth available

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    CCNA3: Switching Basics and Intermediate Routing v3.0

    CISCO NETWORKING ACADEMY PROGRAM

    Chapter 4 Switching Concepts

    Transmission Time & Latency Bit time time taken to recognise 1 bit

    Minimum frame size - 64 bytes 512 bits

    Maximum frame size 1518 bytes 12,144 bits Transmission time is always 512 bit times

    10Mbps 64 byte frame - 51,200 ns (100ns bit time)

    100Mbps 64 byte frame 5,120 ns (10 ns bit time)

    1000Mbps 64 byte frame 512 ns (1ns bit time)

    Times above do not include

    Time taken to propagate signal along medium

    Delays introduced by hubs/switches/routers/NICs etc

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    CCNA3: Switching Basics and Intermediate Routing v3.0

    CISCO NETWORKING ACADEMY PROGRAM

    Chapter 4 Switching Concepts

    Types of TransmissionHalf-duplex

    Host checks mediumfor signal if clear

    host transmits Only 1 host can

    transmit at a time

    Collisions jamsignal generated,

    back-off algorithmbefore retransmission

    50-60% bandwidthavailable

    Full duplex

    Host can transmit

    immediately 2 hosts can transmit

    simultaneously

    No collisions

    100% bandwidthavailable

    Requires dedicatedconnection to aswitchport

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    CCNA3: Switching Basics and Intermediate Routing v3.0

    CISCO NETWORKING ACADEMY PROGRAM

    Switching Concepts

    Introduction to LAN Switching

    Switch Operation

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    CCNA3: Switching Basics and Intermediate Routing v3.0

    CISCO NETWORKING ACADEMY PROGRAM

    Chapter 4 Switching Concepts

    Overview

    Maximum availability for the least cost

    Reduce the effects of collisions on available

    bandwidth Reduce the effect of broadcasts on available

    bandwidth

    Deploy network hardware (media/switches/routers) to

    overcome bottlenecks & meet bandwidthrequirements

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    CCNA3: Switching Basics and Intermediate Routing v3.0

    CISCO NETWORKING ACADEMY PROGRAM

    Chapter 4 Switching Concepts

    LAN Segmentation - bridges A bridge splits a LAN into

    2 segments

    It creates 2 collisiondomains

    Adds 10-30% latency

    Learns MAC addresses

    Keeps local traffic local Forwards broadcasts

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    CCNA3: Switching Basics and Intermediate Routing v3.0

    CISCO NETWORKING ACADEMY PROGRAM

    Chapter 4 Switching Concepts

    LAN Segmentation - Switches Each switchport is a

    collision domainmicro-segmentation

    100% bandwidthavailable to eachswitchport

    Every switchport can

    send/receivesimultaneously

    Host to switch/switch toswitch connection createsfull duplex link

    CISCO NETWORKING ACADEMY PROGRAM

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    CCNA3: Switching Basics and Intermediate Routing v3.0

    CISCO NETWORKING ACADEMY PROGRAM

    Chapter 4 Switching Concepts

    LAN Switch Operation - 1

    When a switch starts up it sends a broadcast out

    of all ports to learn host MAC addresses

    When a frame is received for an unknowndestination a broadcast is sent to discover

    Addresses are added to a switching table

    mapping them to the port on which they werelearned

    When a frame is received for a known

    destination it is switched to the appropriate port

    CISCO NETWORKING ACADEMY PROGRAM

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    CCNA3: Switching Basics and Intermediate Routing v3.0

    CISCO NETWORKING ACADEMY PROGRAM

    Chapter 4 Switching Concepts

    LAN Switch Operation - 2

    Switches contain RAM known as CAM

    Content Addressable Memory

    Stores MAC address table

    Used as frame buffer

    Used to queue frames in asymmetric switching

    switchports operating at different speeds e.g. 10and 100 Mbps

    CISCO NETWORKING ACADEMY PROGRAM

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    CCNA3: Switching Basics and Intermediate Routing v3.0

    CISCO NETWORKING ACADEMY PROGRAM

    Chapter 4 Switching Concepts

    Switching MethodsCut-through Switching

    Fast-forward as soon as destination address is readswitching starts

    Fragment-free after 64 bytes have been received

    (minimum valid frame size) frame is switchedStore & Forward Switching

    Entire frame is received before switching Increased

    Latency

    CISCO NETWORKING ACADEMY PROGRAM

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    CCNA3: Switching Basics and Intermediate Routing v3.0

    CISCO NETWORKING ACADEMY PROGRAM

    Chapter 4 Switching Concepts

    Terminology

    Ignoring a frame filtering

    Copying a frame forwarding

    Microsegmentation dividing a network into

    smaller segments (using a switch)

    CISCO NETWORKING ACADEMY PROGRAM

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    CCNA3: Switching Basics and Intermediate Routing v3.0

    CISCO NETWORKING ACADEMY PROGRAM

    Chapter 4 Switching Concepts

    Broadcasts

    Bridges & switches cannot block layer 2 or layer

    3 broadcasts

    Adding bridges or switches to a network extendsthe broadcast domain but creates additional

    collision domains a 24 port switch creates 24

    collision domains

    Routers can inspect layer 3 packets and create

    broadcast domains a router with 3 ports

    creates 3 broadcast domains