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Layer 2 and Layer 3 Switching

Layer 2 and Layer 3 Switching. Freeha Khan 2 nd Presentation IS 8040 Data Communication Theory and Practice. Switching. Today in data communications, all switching and routing equipment perform two basic operations: Switching data frames Maintenance of switching operations

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Layer 2 and Layer 3 Switching

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  1. Layer 2 and Layer 3 Switching Freeha Khan 2nd Presentation IS 8040 Data Communication Theory and Practice IS8040

  2. Switching • Today in data communications, all switching and routing equipment perform two basic operations: • Switching data frames • Maintenance of switching operations • Switching is the process of taking an incoming frame from one interface and delivering it out through another interface • Routers use Layer 3 switching to route a packet, and switches (Layer 2 switches) use Layer 2 switching to forward frames IS8040

  3. Switches • Switches are similar to bridges but usually have more ports • Switches provide a unique network segment on each port, thereby separating collision domains • Today, network designers are replacing hubs in their wiring closets with switches to increase their network performance and bandwidth while protecting their existing wiring investments IS8040

  4. Switches • 10/100-Mbps Ethernet Switches are good resolution if Ethernet LANs are stretched to the breaking point under the weight of • new users, servers and high-end applications • Most switches provide shared or dedicated 10/100 uplinks to other switches or network backbones, and some even provide one or two dedicated Gigabit Ethernet links for especially heavy bandwidth requirements IS8040

  5. Layer 2 switches, operate at the second, or data link, layer of the open systems interconnection model OSI Model Layer 2 Switching IS8040

  6. Layer 2 Switch Garrett Communications Magnum switches come with eight to 24 10/100-Mbps ports and range in price from $599 to $1,199. IS8040

  7. Layer 2 Switching • Layer 2 switches operate at MAC layer • Layer 2 switches broadcast multicast traffic to all their ports – very detrimental to performance • Static entries can be defined on switches to control multicast at layer 2 but static entries do not react to dynamic behaviors IS8040

  8. Layer 2 Switching • Check incoming network traffic • Keep track of the physical addresses of all stations attached to their ports • Forward traffic to specific station addresses according to the forwarding tables • Layer 2 switches can deliver data at wire speeds because they don’t have to examine individual data packets IS8040

  9. Layer 2 Switching Flow of intersubnet traffic with Layer 2 switches and routers IS8040

  10. Layer 2 Switching • If the Layer 2 switch does not know where to send the frame, it broadcasts the frame out all its ports to the network to learn the correct destination • When the frame's reply is returned, the switch learns the location of the new address and adds the information to the switching table IS8040

  11. Layer 3 switching operates at the network layer OSI Model Layer 3 Switching IS8040

  12. Layer 3 Switch • Limited-purpose • Layer 3 switches are only available for Ethernet • They only route IP/IPX protocols • Capable to perform routing at wire speed: 10, 100, 1000 Mbps IS8040

  13. Layer 3 Switching • Hardware based packet-to-packet IP routing • Hardware based routers cost less than traditional software-based routers • They switch non-routable traffic to Layer 2 IS8040

  14. Layer 3 Switch RapierTM 10/100 Layer 3 Switch IS8040

  15. Layer 3 Switching • It examines packet information and forwards packets based on their network-layer destination addresses • Layer 3 switching also supports router functionality IS8040

  16. Layer 3 Switching Flow of intersubnet traffic with Layer 3 switches IS8040

  17. Difference between Layer 2 and Layer 3 Switches • The difference between Layer 2 and Layer 3 switching is the type of information inside the frame that is used to determine the correct output interface • With Layer 2 switching, frames are switched based on MAC address information • With Layer 3 switching, frames are switched based on network-layer information IS8040

  18. Difference between Layer 2 and Layer 3 Switches • Layer 2 switching does not look inside a packet for network-layer information as does layer 3 switching • Layer 2 switching is performed by looking at a destination MAC address within a frame IS8040

  19. Difference between Layer 2 and Layer 3 Switches • Layer 3 switches looks at the frame's destination address and sends it to the appropriate interface if it knows the destination address location • Layer 2 switching builds and maintains a switching table that keeps track of which MAC addresses belong to each port or interface IS8040

  20. References • Switched, Fast, and Gigabit Ethernet, Robert Breyer and Sean Riley, Third Edition • Business Data Communications, Stallings, Fourth Edition • http://www.gcn.com • http://www.slac.stanford.edu/ • http://www.cisco.com/univercd IS8040

  21. References • http://www.gcn.com/state/vol6_no9/guide/837-2.html • http://www.msic.com IS8040

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