CN_IT2050_Lecture 6_Swith Basics.pdf

IT2050 – Computer Networks Lecture 06 Switched Networks IT2050| Computer Networks| Basics of Switching| Hansika Mahaadikara  Switch An intelligent device Operates in layer 2 – layer2 switch Operates in layer 3 – layer3 switch IT2050| Computer...

IT2050 – Computer Networks Lecture 06 Switched Networks IT2050| Computer Networks| Basics of Switching| Hansika Mahaadikara  Switch An intelligent device Operates in layer 2 – layer2 switch Operates in layer 3 – layer3 switch IT2050| Computer Networks| Basics of Switching| Hansika Mahaadikara  Form Factors Fixed Configuration Modular Configuration Stackable Configuration IT2050| Computer Networks| Basics of Switching| Hansika Mahaadikara Business Considerations 0n Selecting switches Cost Speed and #of Interfaces , Supported Features Expansion Capability Port Density #of devices on the Network Power Power access points , PoE , Redundant Power Supply Reliability 24/7 Continues access Port Speed Ethernet , FastEthernet , GigabitEthernet Scalability Network growth IT2050| Computer Networks| Basics of Switching| Hansika Mahaadikara Switch Functions Address learning Forward/filter decisions Loop avoidance IT2050| Computer Networks| Basics of Switching| Hansika Mahaadikara  Mac Address Table The switch learns the relationship of ports to devices, it builds a table called a MAC address. LAN switches determine how to handle incoming frames by maintaining the MAC address table. Switch builds its MAC address table by recording the MAC address of each device connected to each of its ports. The switch uses the information in the MAC address table to send frames destined for a specific device out the port which has been assigned to that device. IT2050| Computer Networks| Basics of Switching| Hansika Mahaadikara Address learning Layer 2 switches and bridges remember the source MAC address of each frame received on an interface, and they enter this information into a MAC database called a MAC address table IT2050| Computer Networks| Basics of Switching| Hansika Mahaadikara Address learning cont. IT2050| Computer Networks| Basics of Switching| Hansika Mahaadikara Forward/filter decisions When a frame is received on an interface, the switch looks at the destination MAC address and finds the exit interface in the MAC address table Frame is only forwarded out the specified destination port IT2050| Computer Networks| Basics of Switching| Hansika Mahaadikara Forward/filter decisions cont. IT2050| Computer Networks| Basics of Switching| Hansika Mahaadikara Loop Avoidance If multiple connections between switches are created for redundancy purposes, network loops can occur Spanning Tree Protocol (STP) is used to stop network loops while still permitting redundancy IT2050| Computer Networks| Basics of Switching| Hansika Mahaadikara Switch Internal Processing IT2050| Computer Networks| Basics of Switching| Hansika Mahaadikara Switch Internal Processing cont. IT2050| Computer Networks| Basics of Switching| Hansika Mahaadikara Frame Forwarding Store-and-Forward Switching Error Checking– After receiving the entire frame, the switch compares the frame-check-sequence (FCS) value in the last field against its own FCS calculations. Only error-free frames are forwarded Store-and-Forward is Cisco’s primary LAN switching method. IT2050| Computer Networks| Basics of Switching| Hansika Mahaadikara Frame Forwarding Cut-Through Switching Cut – Through Switching ( Rapid Frame Forwarding ) – The switch makes a forwarding decision as soon as it has looked up the destination MAC address. Frames with errors are forwarded. IT2050| Computer Networks| Basics of Switching| Hansika Mahaadikara  Frame Forwarding Fragment Free Switching Fragment Free - modified form of cut-through switching. The switch waits for the collision window (64 bytes) to pass before forwarding the frame. Provides better error checking than cut-through, with practically no increase in latency. IT2050| Computer Networks| Basics of Switching| Hansika Mahaadikara Basic Switch Configurations Each port/interface does not need an IP address because the switch is not performing Layer 3 routing Can assign IP address to manage the switch or else IP would not be needed on the switch at all IT2050| Computer Networks| Basics of Switching| Hansika Mahaadikara Configuring Basic Switch Management Access with IPv4 exit Important Concept The default gateway is the router address and is used by the switch to communicate with other networks. IT2050| Computer Networks| Basics of Switching| Hansika Mahaadikara Configure Switch Ports Verifying Switch Port Configuration IT2050| Computer Networks| Basics of Switching| Hansika Mahaadikara IT2050| Computer Networks| Basics of Switching| Hansika Mahaadikara