CSCO 272 VLANs

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CSCO 272VLANs

• LAN Switching and Wireless Chapter 3

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Objectives

• Explain the role of VLANs in a converged network.
  
• Explain the role of trunking VLANs in a converged
  network.
• Configure VLANs on the switches in a converged
  network topology.
• Troubleshoot the common software or hardware
  misconfigurations associated with VLANs on
  switches in a converged network topology.

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Introduction to VLAN

• 3.1.1
• How can the network accommodate the shared needs
  of the geographically separated departments?
• Do you create a large LAN and wire each
  department together?
• How easy would it be to make changes to that
  network?

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Introduction to VLAN

• It would be great to group the people with the
  resources they use regardless of their geographic
  location, and it would make it easier to manage
  their specific security and bandwidth needs.

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What is VLAN?

• A VLAN allows a network administrator to create
  groups of logically networked devices that act as
  if they are on their own independent network
• A VLAN is a logically separate IP subnetwork.
• VLANs allow multiple IP networks and subnets to
  exist on the same switched network.

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Explain the Role of VLANs in a Converged Network
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Explain the Role of VLANs in a Converged Network
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Benefits of VLAN

• Security
• Cost Reduction
• Higher Performance
• Broadcast mitigation
• Improved IT staff efficiency
• Simpler project or application management

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VLAN
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Types of VLAN

• 3.1.2
• Data VLAN
• Configured to carry only user-generated traffic.
• It is common practice to separate voice and
  management traffic from data traffic.
• a "data VLAN". A data VLAN is sometimes referred
  to as a user VLAN.

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Types of VLAN contd..

• Default VLAN
• All switch ports become a member of the default
  VLAN after the initial boot up of the switch.
• same broadcast domain.
• The default VLAN for Cisco switches is VLAN 1.
• VLAN 1 has all the features of any VLAN, except
  that you cannot rename it and you can not delete
  it.
• Layer 2 control traffic, such as CDP and spanning
  tree protocol traffic, will always be associated
  with VLAN 1 - this cannot be changed

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Default VLAN

• It is a security best practice to change the
  default VLAN to a VLAN other than VLAN 1
• This entails configuring all the ports on the
  switch to be associated with a default VLAN other
  than VLAN 1.

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Native VLAN

• A native VLAN is assigned to an 802.1Q trunk
  port.
• An 802.1Q trunk port supports traffic coming from
  many VLANs (tagged traffic) as well as traffic
  that does not come from a VLAN (untagged
  traffic).
• The 802.1Q trunk port places untagged traffic on
  the native VLAN.

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Native VLAN

• Native VLANs are set out in the IEEE 802.1Q
  specification to maintain backward compatibility
  with untagged traffic common to legacy LAN
  scenarios

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Management VLAN

• A management VLAN is any VLAN you configure to
  access the management capabilities of a switch.
• VLAN 1 would serve as the management VLAN if you
  did not proactively define a unique VLAN to serve
  as the management VLAN.

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Management VLAN

• A switch can be managed via HTTP, Telnet, SSH, or
  SNMP.
• you wouldn't want an arbitrary user connecting to
  a switch to default to the management VLAN.

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Voice VLAN

• Voice Traffic requires
• Assured bandwidth to ensure voice quality
• Transmission priority over other types of network
  traffic
• Ability to be routed around congested areas on
  the network
• Delay of less than 150 milliseconds (ms) across
  the network

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Switch Port Membership

• Switch ports are Layer 2-only interfaces
  associated with a physical port.
• Switch ports are used for managing the physical
  interface and associated Layer 2 protocols.
• Can not support routing or bridging.
• Switch ports belong to one or more VLANs.

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Static VLAN

• Ports on a switch are manually assigned to a
  VLAN.

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Dynamic VLAN

• This mode is not widely used in production
  networks and is not explored in this course.
• A dynamic port VLAN membership is configured
  using a special server called a VLAN Membership
  Policy Server (VMPS).
• With the VMPS, you assign switch ports to VLANs
  dynamically, based on the source MAC address of
  the device connected to the port

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Voice VLAN

• A port is configured to be in voice mode so that
  it can support an IP phone attached to it.
• Before you configure a voice VLAN on the port,
  you need to first configure a VLAN for voice and
  a VLAN for data.

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Controlling Broadcast Domain within VLAN

• When VLANs are implemented on a switch, the
  transmission of unicast, multicast, and broadcast
  traffic from a host on a particular VLAN are
  constrained to the devices that are on the VLAN.
• 3.1.4
• 3.1.5

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Layer 3 Switch

• Switch virtual interface (SVI) technology that
  allows a Layer 3 switch to route transmissions
  between VLANs.
• A Layer 3 switch has the ability to route
  transmissions between VLANs.
• 3.1.4

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VLAN Trunk

• A trunk is a point-to-point link between two
  network devices that carries more than one VLAN.
• A VLAN trunk allows you to extend the VLANs
  across an entire network. Cisco supports IEEE
  802.1Q for coordinating trunks on Fast Ethernet
  and Gigabit Ethernet interfaces.
• A VLAN trunk does not belong to a specific VLAN,
  rather it is a conduit for VLANs between switches
  and routers.
• You will learn about 802.1Q later in this
  section.

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Explain the Role of Trunking VLANs in a Converged
Network
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802.1Q Frame Tagging

• When the switch receives a frame on a port
  configured in access mode with a static VLAN, the
  switch takes apart the frame and inserts a VLAN
  tag, recalculates the FCS and sends the tagged
  frame out a trunk port.

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VLAN Tag Field Details

• 3.2.1

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VLAN Trunk
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VLAN Trunking Operation

• 3.2.2

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Trunking Modes ( ISL or IEEE)

• An IEEE 802.1Q trunk port supports simultaneous
  tagged and untagged traffic.
• An 802.1Q trunk port is assigned a default PVID,
  and all untagged traffic travels on the port
  default PVID.
• All untagged traffic and tagged traffic with a
  null VLAN ID are assumed to belong to the port
  default PVID.
• A packet with a VLAN ID equal to the outgoing
  port default PVID is sent untagged. All other
  traffic is sent with a VLAN tag.

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ISL

• In an ISL trunk port, all received packets are
  expected to be encapsulated with an ISL header,
  and all transmitted packets are sent with an ISL
  header.
• Native (non-tagged) frames received from an ISL
  trunk port are dropped. I
• SL is no longer a recommended trunk port mode,
  and it is not supported on a number of Cisco
  switches.

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Configure VLANs on the Switches in a Converged
Network Topology
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Configure VLANs on the Switches in a Converged
Network Topology
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Configure VLANs on the Switches in a Converged
Network Topology
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Assign Switch Port

• 3.3.2

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Verification commands

• show vlan brief
• show vlan name student
• show vlan summary
• 3.3.3

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Managing VLAN

• 3.3.3
• Reassign a port to a different VLAN
• Deleting a VLAN
• no vlan vlan-id ( global configuration mode)
• Deleting a VLAN database
• delete flashvlan.dat
• Erasing running-configuration file will not
  delete a VLAN database

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Trunk Port Configuration

• 3.3.4
• Verifying Trunk port configuration
• show interfaces interface-ID switchport

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Common Problems with Trunk Port

• Native VLAN Mismatches
• Trunk Mode mismatches
• VLAN and IP subnets
• Allowed VLAN on Trunks

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Troubleshoot Common Software or Hardware
Misconfigurations Associated with VLANs
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Troubleshoot Common Software or Hardware
Misconfigurations Associated with VLANs
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Troubleshoot Common Software or Hardware
Misconfigurations Associated with VLANs
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Summary

• VLANS
• Allows an administrator to logically group
  devices that act as their own network
• Are used to segment broadcast domains
• Some benefits of VLANs include
• Cost reduction, security, higher Performance,
  better management

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Summary

• Types of Traffic on a VLAN include
• Data
• Voice
• Network protocol
• Network management
• Communication between different VLANs requires
  the use of
• Routers

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Summary

• Trunks
• A common conduit used by multiple VLANS for
  intra-VLAN communication
• EEE 802.1Q
• The standard trunking protocol
• Uses frame tagging to identify the VLAN to which
  a frame belongs
• Does not tag native VLAN traffic