Internetworking devices(networking)
- 1. 1© 2009, Cisco Systems, Inc. All rights reserved. Module 2 Internetworking Devices By Dr. Percy DIAS
- 2. 2 Physical Topology • Physical topology is the actual layout of the wire or media.
- 3. 3 Physical Topology • Bus –Connects all the devices using a single cable –Main cable segment must end with a terminator that absorbs the signal when it reaches the end (data can bounces back) • Star –Most commonly used in Ethernet LAN –Central connection point can be a hub, switch or router, and might be desirable for security or restricted access –If the central device fails, the whole network becomes disconnected
- 4. 4 Physical Topology • Ring –Frame travels around the ring, stopped at each node –If a node wants to transmit data, it is permitted to add data as well as destination address –Each device cleans up the signal, so fewer repeaters are needed
- 5. 5 Physical Topology • Dual Ring –If one ring fails, data can be transmitted on the other ring • Full-mesh –Connect all devices to each other for redundancy and fault tolerance • Partial-mesh –At least one device maintains multiple connections to others
- 6. 6 Logical Topology • Logical topology of a network refers to the logical paths that signals travel from one point on the network to another • Broadcast – Ethernet • Token Passing – Controls network access by passing an electronic token sequentially to each host – Token Ring and FDDI are examples of Token Passing on a physical ring topology
- 7. 7 Collisions • Hubs operate at Layer 1, simply repeating all received signals out all other ports
- 8. 8 Networking Devices • End user devices – Provide services directly to the user • Network devices – Connect the end-user devices to allow them to communicate • Data leaves a source and it is transformed into either electrical , light pulse or radio waves (signals) that pass along the medium
- 11. 11 Repeated Ethernet Signal • Betty sends a clean signal • The signal degrades by the time it reaches the repeater • The repeater regenerates a new, clean signal and sends it out its other port
- 12. 12 Repeaters • When a signal is sent over a wire, it degrades • To extend the distance of LANs, repeaters were developed • Typically had two ports connecting two different Ethernet segments • Interpreted the incoming signal on one port as 1’s and 0’s • Sent a regenerated clean signal out the other port
- 14. 14 Hubs • Regenerate signals • Used as network concentration points • Multiport repeater • Layer 1 device
- 15. 15 Hub Operation
- 16. 16 Network Interface Card • Carries a unique code called a Media Access Control (MAC) • MAC address controls data communication for the host on the network • NICs are considered layer 2 and operate at both layer 1 and 2 (Layer 1: send and receive signals over an attached cable)
- 17. 17 Bridges Layer 2 device designed to create two or more LAN segments, each of which is a separate collision domain Bridges filter traffic by looking at MAC addresses.
- 18. 18 Bridges • Filter traffic on a LAN to keep local traffic local yet allow connectivity to other parts • Keep track of which MAC addresses are on each side of the bridge and makes forwarding decisions based on MAC address table • When a bridge receives a frame, the destination MAC address is looked up in the bridge table to determine whether to filter, flood or forward the frame onto another segment.
- 19. 19 Bridges
- 21. 21 Learning Table Entries and Flooding Unknown Unicasts • Switches and bridges learn entries in the table dynamically • They use this logic: – Examine the source MAC address of the frame and the interface on which it was received – Add that source MAC address and corresponding interface to the table
- 22. 22 Learning Content Addressable Memory (CAM) Table Entries: Two Switches SW2
- 23. 23 Bridge Making Filter Decision
- 24. 24 Bridge Making a Forwarding Decision
- 25. 25 LAN Switches • Layer 2 device • Use a table of MAC addresses (switching table) to determine the segment on which a frame needs to be transmitted • Cisco switching table sometimes referred to as Content Addressable Memory (CAM). • Switches operate at much higher speed than bridges (hardware vs software) • Each switch port acts as a separate bridge and give each host the medium’s full bandwidth (microsegmentation) • Improve network performance: speed and bandwidth
- 26. 26 Switch Making a Forwarding Decision
- 27. 27
- 29. 29 Preventing Collisions with Switch Buffering • Switches prevent collisions by buffering frames • If several PCs send frames to the same address at the same time, the switch holds the frames in memory - a process called buffering • The switch then forwards the frames one at a time
- 30. 30 Routers • Layer 3 device • Use logical address (network layer address) • Can connect different layer 2 technologies • Examine incoming packet (layer 3 data), choose the best path, and switch them to the proper outgoing port.
- 31. 31 Cisco Academy 3 Reference • CCNA1 Online Materials • Slide 2 - 6: 2.1.4 • Slide 8-9, 26: 2.1.3 • Slide 12-14: 5.1.6-5.1.7 • Slide 16-19, 23-24, 26: 5.1.9-5.1.11
- 32. 32 Cisco Academy 4 Exploration Reference Networking Fundamentals • Slide 2 - 6: 9.1.1-9.1.3 • Slide 8-9,12-14, 26: 9.6.1-9.6.4 • Slide 16-19, 23-24, 26: 9.6.1-9.6.4 • Slide 14-15: 9.6.1-9.6.2