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Chabot College

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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? – PowerPoint PPT presentation

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Title: Chabot College


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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