CCNA3: Switching Basics and Intermediate Routing v3.0 CISCO NETWORKING ACADEMY PROGRAM Switching Concepts Introduction to Ethernet/802.3 LANs Introduction to LAN Switching Switch Operation

CCNA3: Switching Basics and Intermediate Routing v3.0 CISCO NETWORKING ACADEMY PROGRAM Switching Concepts Introduction to Ethernet/802.3 LANs

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

CCNA3: Switching Basics and Intermediate Routing v3.0 CISCO NETWORKING ACADEMY PROGRAM Chapter 4 – Switching Concepts Network Growth Bandwidth needs have increased –Internet/intranet/ –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!

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/bandwidth domain Broadcasts propagated out of every port Only 1 device can transmit at a time Only 50-60% bandwidth available thick Ethernet or thin Ethernet infrastructures

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/bandwidth domains Broadcasts are forwarded Local traffic stays local Checks Layer 2 MAC addresses in frame

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 of every port Each switchport has dedicated bandwidth 100% bandwidth available

CCNA3: Switching Basics and Intermediate Routing v3.0 CISCO NETWORKING ACADEMY PROGRAM Chapter 4 – Switching Concepts Today’s LANs Router

CCNA3: Switching Basics and Intermediate Routing v3.0 CISCO NETWORKING ACADEMY PROGRAM Chapter 4 – Switching Concepts Elements of Ethernet/802.3 networks Broadcast data frame delivery of Ethernet/802.3 The carrier sense multiple access/collision detect (CSMA/CD) method allows only one station to transmit at a time. Multimedia applications with higher bandwidth demand such as video and the Internet, coupled with the broadcast nature of Ethernet, can create network congestion. Normal latency as the frames travel across the layers Extending the distances and increasing latency of the Ethernet/802.3 LANs by using Layer 1 repeaters.

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

CCNA3: Switching Basics and Intermediate Routing v3.0 CISCO NETWORKING ACADEMY PROGRAM Chapter 4 – Switching Concepts Types of Transmission Half-duplex Host checks medium for signal – if clear host transmits Only 1 host can transmit at a time Collisions – jam signal generated, back-off algorithm before retransmission 50-60% bandwidth available Full duplex Host can transmit immediately 2 hosts can transmit simultaneously No collisions 100% bandwidth available Requires dedicated connection to a switchport

CCNA3: Switching Basics and Intermediate Routing v3.0 CISCO NETWORKING ACADEMY PROGRAM Switching Concepts Introduction to LAN Switching Switch Operation

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 bandwidth requirements

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 collision domains Adds 10-30% latency Learns MAC addresses Keeps local traffic local Forwards broadcasts

CCNA3: Switching Basics and Intermediate Routing v3.0 CISCO NETWORKING ACADEMY PROGRAM Chapter 4 – Switching Concepts LAN Segmentation With Bridges Segmentation provides fewer uses per segment Bridges store, then forward frames based on Layer 2 addresses (CRC verified) Layer 3 protocol-independent Increase latency on the network

CCNA3: Switching Basics and Intermediate Routing v3.0 CISCO NETWORKING ACADEMY PROGRAM Chapter 4 – Switching Concepts LAN Segmentation - Switches Each switchport is a collision domain – “micro- segmentation” 100% bandwidth available to each switchport Every switchport can send/receive simultaneously Host to switch/switch to switch connection creates full duplex link

CCNA3: Switching Basics and Intermediate Routing v3.0 CISCO NETWORKING ACADEMY PROGRAM Chapter 4 – Switching Concepts LAN Segmentation With Routers More manageable, greater functionality, multiple active paths Smaller broadcast domains Operates at Layer 3

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 unknown destination a broadcast is sent to discover Addresses are added to a switching table mapping them to the port on which they were learned When a frame is received for a known destination it is switched to the appropriate port

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. 10 and 100 Mbps

CCNA3: Switching Basics and Intermediate Routing v3.0 CISCO NETWORKING ACADEMY PROGRAM Chapter 4 – Switching Concepts Switching Methods Cut-through Switching Fast-forward – as soon as destination address is read switching starts Fragment-free – after 64 bytes have been received (minimum valid frame size) frame is switched Store & Forward Switching Entire frame is received before switching Increased Latency

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)

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 extends the 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