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Chabot College

Chabot College. ET 99.09 Cisco Semester 3 Chapter 3 VLANs M. McGregor, Los Medanos College, Pittsburg, CA. Introduction to VLANs. What is a VLAN?. Why create VLANs?. Switches are the core of VLANs. VLAN Switching and Filtering.

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Chabot College

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  1. Chabot College ET 99.09 Cisco Semester 3 Chapter 3 VLANs M. McGregor, Los Medanos College, Pittsburg, CA

  2. Introduction to VLANs

  3. What is a VLAN?

  4. Why create VLANs?

  5. Switches are the core of VLANs

  6. VLAN Switching and Filtering Each switch has the intelligence to make filtering and forwarding decisions by frame, based on VLAN metrics defined by network managers, and to communicate this information to other switches and routers within the network.

  7. Frame filtering and tagging The most common approaches for logically grouping users into distinct VLANs are: • frame filtering • frame tagging

  8. Frame Filtering

  9. Tradeoffs with frame filtering • Filter-based VLANs do not scale well because each frame has to be referenced to a lookup table. • The IEEE 802 committee has adopted frame tagging as the standard because it is more scalable.

  10. IEEE 802 VLAN Standardization

  11. Frame Tagging

  12. VLAN Flexibility

  13. Problems with broadcasts

  14. Problems with broadcasts When no routers are placed between switches, broadcasts (Layer 2 transmissions) are sent to every switched port. This is commonly referred to as a “flat” network where there is one broadcast domain across the entire network

  15. VLANs can control broadcasts

  16. VLANs can provide security

  17. VLANs provide flexibility

  18. Where are the routers? Layer 3 communication, either embedded in the switch or provided externally, is an integral part of any high-performance switching architecture.

  19. What are hubs good for?

  20. Leveraging your investment

  21. Port-Centric VLANs

  22. Port-centric VLANs VLAN Membership by port maximizes forwarding performance because: • Users are assigned by port. • VLANs are easily administered • Maximizes security between VLANs • Packets do not “leak” into other domains • VLANs and membership are easily controlled across network

  23. Static VLANs

  24. Dynamic VLANs Dynamic VLANs are ports on a switch that can automatically determine their VLAN assignments.

  25. VLANs across backbones

  26. VLANs across backbones • Fast Ethernet - ISL (Inter-Switch Link) • FDDI - IEEE 802.10 • ATM - LAN Emulation (LANE)

  27. VTP - VLAN Trunk Protocol • VTP Domain • VTP Configuration revision number • VLAN IDs (ISL) • Emulated LAN names (ATM) • 802.10 SAID values (FDDI) • MTU • Frame format • VLAN configuration

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