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Configuring your VLAN


Configuring your VLAN Presented by Gregory Laffoon * Questions & Answers * Overview of Networking Terms Networking Terms Overview OSI Model Defines a networking ... – PowerPoint PPT presentation

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Title: Configuring your VLAN

Configuring your VLAN
Presented by Gregory Laffoon
Overview of Networking Terms
Networking Terms Overview
  • OSI Model
  • Defines a networking framework for implementing
    protocols in seven layers
  • Control is passed from one layer to the next,
    starting at the application layer in one station,
    proceeding to the bottom layer, over the channel
    to the next station and back up the hierarchy

OSI Model
  • Of the 7 layers, we are concerned with the bottom
    3 layers.
  • The top 4 layers are used more on host machines
    to support TCP/UDP, HTTP, other applications

OSI Models
  • OSI Layer 1
  • This layer is the transmission media
  • Category 5e and fiber optic cabling
  • Radio signal in terms of wireless
  • Performs transmission of raw bits

OSI Models
  • OSI Layer 2
  • Data packets are encoded and decoded into bits.
  • Divided into 2 sub-layers
  • MAC (Media Access Control)
  • Controls how hosts on the network gain access to
    the data and permission to transmit it
  • LLC (Logical Link Control)
  • Controls frame synchronization, flow control, and
    error checking

OSI Models
  • OSI Layer 3
  • Routing and forwarding functions
  • Handles end to end addressing
  • Provides the mean for separate networks to talk
    to each other
  • IP (Internet Protocol) is at this level

Definition of Network Device Types
Network Device Types
  • There are 5 general devices
  • Repeater
  • Hub
  • Bridge
  • Switch
  • Router

Network Device - Repeater
  • Repeater
  • A Layer 1 device
  • An electronic device to receive a signal on a
    port and retransmits it at a higher level or
    higher power
  • Used when you need to go farther distances than
    the cabling will allow
  • Usually has 2 ports (IN/OUT)

Network Device - Hub
  • Hub
  • A Layer 1 device
  • A device that contains multiple ports
  • Has no logic or brain
  • Simply passes data out all other ports
  • In simple terms, it is a multi-port repeater

Network Device - Bridge
  • Bridge
  • A Layer 2 device
  • Connects multiple Layer 2 segments
  • Has logic or brain
  • Learns what Layer 2 MAC addresses are associated
    with each port
  • Receives frames destined for a particular MAC
    address and only sends the data out the correct

Network Device - Switch
  • Switch
  • A layer 2 device
  • Basically a multi-port bridge
  • Learns MAC Addresses to Port mappings
  • Doesnt flood data out every port unless the MAC
    address hasnt been learned

Network Device - Router
  • Router
  • A Layer 3 device
  • Connects multiple Layer 3 networks
  • Uses Layer 3 addressing (IP addressing)
  • Allows communication between different Layer 2
  • Breaks up broadcast domains

Broadcast Domain?
  • A broadcast domain is a network segment in which
    any network device can transmit data directly to
    another device without going through a router
  • A layer 3 device breaks up a broadcast domain

So what is a VLAN?
What is a VLAN?
  • A virtual local area network (VLAN) is a group of
    hosts with a common set of requirements that
    communicate as if they were attached to the same
    broadcast domain regardless of their physical

Traditional LAN
  • A traditional LAN would require all users of the
    same requirements and same IP subnet (broadcast
    domain) be connected to the same equipment.

VLAN-based LAN
  • By utilizing VLANs, the same users can be spread
    out over various geographical locations and still
    remain in their same IP subnet (broadcast domain).

How VLANs work?
How VLANs Work?
  • VLANs are identified by a number
  • Valid ranges 1-4094
  • On a VLAN-capable switch, you assign ports with
    the appropriate VLAN number
  • The switch then only allows data to be sent
    between ports with the same VLAN

How VLANs Work?
  • Since almost every network is larger than a
    single switch, there needs to be a way to have
    traffic sent between two different switches
  • One way to do it is to assign a port on each
    switch with a VLAN and run a cable between the
  • Not very feasible or cost effective

How VLANs work?
  • For example, if there were 6 hosts on each switch
    on 6 different vlans, you would need 6 ports on
    each switch to connect the switches together.
    This would mean that if you had 24 different
    vlans you could only have 24 hosts on a 48 port

How VLANs work?
  • There was a standard develop to make it so that a
    single connection between two switches could be
    used to send traffic for all vlans
  • 802.1q Provides a VLAN tag in front of the
    Layer 2 frame

How VLANs work?
  • You enable 802.1q tagging (trunking) on the ports
    between the switches
  • The switch receives the frame with the 802.1q
    header and strips it off
  • It determines what VLAN and sends the data to the
    appropriate port

Benefits of VLANs
Benefits of VLANs
  • Geographically separated users on the same IP
    subnet (broadcast domain)
  • Limit the size of broadcast domains and limit
    broadcast activity
  • Security benefits by keep hosts separated by VLAN
    and limiting what devices can talk to those hosts

Benefits of VLANs
  • Cost savings as you dont need additional
    hardware and cabling
  • Operational benefits because changing a users IP
    subnet (Broadcast Domain) is in software

Drawbacks of VLANs
  • VLANs were used to allow grouping of users
    together with the same requirements and allowing
    them to be in separate locations
  • The major drawback is that the general idea is to
    make all users that need the same requirements be
    in the same VLAN

Drawbacks of VLANs
  • VLANs work at Layer 2 and that layer doesnt
    handle redundancy in an efficient manner
  • So when the network becomes mission critical, it
    is hard to provide fast convergence times for
    users when utilizing VLANs that span across
    multiple buildings

Drawbacks of VLANs
  • VLANs were and still are a viable method for
    separating users into groups
  • Today, redundancy is very important so to make
    the network stable the following guidelines
    should be followed

Drawbacks of VLANs
  • VLANs should still be used to separate and group
    common users
  • VLANs shouldnt span across the entire network
  • They should remain in a building
  • Common users in another building should be on a
    separate VLAN

Drawbacks of VLANs
  • Then the two common user groups would utilize a
    router to talk to each other

Questions Answers
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