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Questions and Answers

What happens to the frequency of broadcasts as the number of peers on a network grows?

  • It becomes unpredictable
  • It remains the same
  • It increases (correct)
  • It decreases

    • What is the primary function of VLANs in managing broadcast traffic?

  • To break up a large network into smaller independent segments (correct)
  • To bridge network traffic between VLANs
  • To increase the amount of broadcast traffic
  • To merge multiple networks into a single network

    • What is the relationship between VLANs and IP subnets?

  • VLANs and IP subnets are unrelated
  • There is always a one-to-one relationship between VLANs and IP subnets
  • One VLAN can have multiple subnets (correct)
  • One subnet can have multiple VLANs

    • What is a limitation of networks without VLAN capability?

    <p>Users are limited by physical topologies and distances</p> Signup and view all the answers

    What is a benefit of using VLANs?

    <p>It decouples the users' network location from their physical location</p> Signup and view all the answers

    What OSI layer do VLANs belong to?

    <p>Data link layer (OSI layer 2)</p> Signup and view all the answers

    What is a benefit of using VLANs in a network?

    <p>Simplified administration</p> Signup and view all the answers

    Which of the following is NOT a common use case for VLANs?

    <p>Database management</p> Signup and view all the answers

    What is a potential security risk of VLANs if not implemented carefully?

    <p>They can be defeated</p> Signup and view all the answers

    What is a benefit of using VLANs in cloud computing?

    <p>Mitigating security issues</p> Signup and view all the answers

    Which network technology does NOT have VLAN capabilities?

    <p>Wi-Fi</p> Signup and view all the answers

    What was the limitation of early Ethernet networks?

    <p>Limited distance between nodes to a few hundred feet</p> Signup and view all the answers

    Who began addressing the problem of scaling up Ethernet networks?

    <p>Dr. W. David Sincoskie</p> Signup and view all the answers

    What was the estimated total bandwidth of the telephone network in the 1980s?

    <p>1 Tbit/s</p> Signup and view all the answers

    What is the command to remove a VLAN?

    <p>no vlan</p> Signup and view all the answers

    What is the VLAN number that was created in the initial configuration?

    <p>3</p> Signup and view all the answers

    What is the command to save the configuration?

    <p>wr</p> Signup and view all the answers

    What is the command to verify the VLAN configuration?

    <p>show vlan brief</p> Signup and view all the answers

    What is the name of the VLAN that is assigned to ports Fa0/14, Fa0/15, and Fa0/16?

    <p>CSC</p> Signup and view all the answers

    What is the status of VLAN 3 in the given configuration?

    <p>active</p> Signup and view all the answers

    What is the name of the VLAN that is assigned to ports Fa0/1, Fa0/2, and Fa0/3?

    <p>default</p> Signup and view all the answers

    What is the purpose of configuring Voice and Data VLAN on ports connected to phones?

    <p>To prioritize voice traffic</p> Signup and view all the answers

    What is the status of VLAN 10 and VLAN 11?

    <p>Active</p> Signup and view all the answers

    Which interfaces are associated with VLAN 10?

    <p>Fa0/1, Fa0/2, Fa0/3, Fa0/4</p> Signup and view all the answers

    What is the operational mode of the Fa0/4 interface?

    <p>Static access</p> Signup and view all the answers

    What is the voice VLAN of the Fa0/4 interface?

    <p>VLAN 11</p> Signup and view all the answers

    What is the administrative mode of the Fa0/4 interface?

    <p>Static access</p> Signup and view all the answers

    What is the access mode VLAN of the Fa0/4 interface?

    <p>VLAN 10</p> Signup and view all the answers

    What is the trunking native mode VLAN of the Fa0/4 interface?

    <p>VLAN 1</p> Signup and view all the answers

    What layer of the OSI model do VLANs operate on?

    <p>Data link layer</p> Signup and view all the answers

    What is the maximum number of VLANs supported by IEEE 802.1Q?

    <p>4094</p> Signup and view all the answers

    What is the purpose of Cisco's Inter-Switch Link (ISL) protocol?

    <p>To interconnect switches and maintain VLAN information</p> Signup and view all the answers

    What is the main difference between ISL and IEEE 802.1Q tagging?

    <p>ISL uses external tagging, while IEEE 802.1Q uses internal tagging</p> Signup and view all the answers

    What is the purpose of VLAN Trunking Protocol (VTP)?

    <p>To propagate VLAN definitions on the whole local area network</p> Signup and view all the answers

    What is the limitation of the number of IP subnets in a VLAN?

    <p>A single VLAN can contain multiple IP subnets</p> Signup and view all the answers

    What is the extension of IEEE 802.1Q that adds support for multiple, nested VLAN tags?

    <p>IEEE 802.1ad</p> Signup and view all the answers

    What is the limitation of the number of VLANs in IEEE 802.1Q when using the Shortest Path Bridging feature?

    <p>16 million</p> Signup and view all the answers

    Why is ISL proprietary protocol deprecated?

    <p>Because it is not widely supported by other vendors</p> Signup and view all the answers

    What does VLAN stand for?

    <p>Virtual Local Area Network</p> Signup and view all the answers

    At what OSI layer do VLANs operate?

    <p>OSI layer 2</p> Signup and view all the answers

    What is the purpose of VLAN tagging?

    <p>To provide network segmentation</p> Signup and view all the answers

    What is a benefit of using VLANs?

    <p>Improved network scalability</p> Signup and view all the answers

    What can be used to route data efficiently in VLAN trunks?

    <p>Link aggregation</p> Signup and view all the answers

    What do routers between VLANs do?

    <p>All of the above</p> Signup and view all the answers

    What is the purpose of setting up VLANs?

    <p>To provide network segmentation</p> Signup and view all the answers

    What is a result of using VLANs?

    <p>Multiple broadcast domains</p> Signup and view all the answers

    What happens when a large network is broken up into smaller independent segments?

    <p>The amount of broadcast traffic each network device and segment has to bear decreases</p> Signup and view all the answers

    What is the primary purpose of VLANs in a network?

    <p>To create multiple layer 3 networks on a single physical infrastructure</p> Signup and view all the answers

    What is the benefit of using VLANs in terms of user location?

    <p>Users can be logically grouped regardless of their physical location</p> Signup and view all the answers

    What is the effect of switches bridging network traffic between VLANs?

    <p>It violates the integrity of the VLAN broadcast domain</p> Signup and view all the answers

    What is the relationship between VLANs and IP subnets?

    <p>One VLAN can have multiple IP subnets, but not vice versa</p> Signup and view all the answers

    What is the layer of the OSI model that VLANs operate on?

    <p>Data link layer</p> Signup and view all the answers

    What is the primary benefit of using VLANs in a network?

    <p>To improve network scalability</p> Signup and view all the answers

    What happens to broadcast traffic in a network as the number of peers grows?

    <p>The frequency of broadcasts increases</p> Signup and view all the answers

    What was the main limitation of using IP routing to connect multiple Ethernet networks together?

    <p>High cost and relatively slow speed</p> Signup and view all the answers

    What is the purpose of adding a tag to each Ethernet frame in VLANs?

    <p>To enable switches to handle frames of a single color</p> Signup and view all the answers

    What is the result of using a mix of different frame colors in a multitree bridge?

    <p>Improved aggregate bandwidth</p> Signup and view all the answers

    Who is credited with inventing VLANs?

    <p>Sincoskie</p> Signup and view all the answers

    What is the standard that describes Ethernet VLANs?

    <p>IEEE 802.1Q-1998</p> Signup and view all the answers

    What is the purpose of the IEEE 802.1ad standard?

    <p>To allow nested VLAN tags</p> Signup and view all the answers

    What problem were early Ethernet networks limited by?

    <p>High cost and relatively slow speed</p> Signup and view all the answers

    What is the result of centrally locating switches in a network?

    <p>Centrally located switches become bottlenecks</p> Signup and view all the answers

    What is the purpose of the 'switchport voice vlan' command?

    <p>To configure a voice VLAN on a port</p> Signup and view all the answers

    What is the status of VLAN 1 in the given configuration?

    <p>Active</p> Signup and view all the answers

    What is the VLAN number that is associated with the interfaces Fa0/1, Fa0/2, Fa0/3, and Fa0/4?

    <p>VLAN 10</p> Signup and view all the answers

    What is the command to verify the VLAN configuration?

    <p>show vlan brief</p> Signup and view all the answers

    What is the purpose of the 'switchport mode access' command?

    <p>To configure an access interface</p> Signup and view all the answers

    What is the operational mode of the Fa0/4 interface?

    <p>Static access</p> Signup and view all the answers

    What is the command to save the configuration?

    <p>wr</p> Signup and view all the answers

    What is the trunking native mode VLAN of the Fa0/4 interface?

    <p>VLAN 1</p> Signup and view all the answers

    What is a common use of VLANs in network administration?

    <p>To simplify network administration</p> Signup and view all the answers

    What type of traffic can be optimized on VLAN trunk links?

    <p>VoIP and SAN traffic</p> Signup and view all the answers

    What is a potential security risk of VLANs?

    <p>VLANs can be defeated if not implemented carefully</p> Signup and view all the answers

    Which of the following network technologies does NOT have VLAN capabilities?

    <p>Wi-Fi</p> Signup and view all the answers

    What was the limitation of early Ethernet networks?

    <p>All of the above</p> Signup and view all the answers

    What was Dr. W.D. David Sincoskie trying to address?

    <p>The limitation of early Ethernet networks</p> Signup and view all the answers

    How do VLANs help in cloud computing?

    <p>By providing a measure of security</p> Signup and view all the answers

    What is a benefit of using VLANs in a network?

    <p>Improved network scalability</p> Signup and view all the answers

    What mechanism is used to create Switched VLANs?

    <p>IEEE 802.1ad frames with S Tag</p> Signup and view all the answers

    What is the command to create a VLAN?

    <p>Switch(config)#vlan 2</p> Signup and view all the answers

    What is the purpose of the command 'Switch(config-if)#switchport access vlan 2'?

    <p>To assign VLAN 2 to a port</p> Signup and view all the answers

    What is the status of VLAN 2 in the given configuration?

    <p>Active</p> Signup and view all the answers

    What is the command to verify the VLAN configuration?

    <p>Switch#show vlan brief</p> Signup and view all the answers

    What is the name of the VLAN assigned to ports Fa0/14, Fa0/15, and Fa0/16?

    <p>CSC</p> Signup and view all the answers

    What is the result of attempting to assign a VLAN that does not exist?

    <p>An error message is displayed</p> Signup and view all the answers

    What is the purpose of configuring multiple ports for a VLAN?

    <p>To assign a VLAN to multiple ports</p> Signup and view all the answers

    What is the primary function of a VLAN in a computer network?

    <p>To partition and isolate a broadcast domain</p> Signup and view all the answers

    What is the benefit of using a VLAN trunk?

    <p>To route data efficiently and use link aggregation</p> Signup and view all the answers

    What is the main purpose of setting up VLANs?

    <p>To provide network segmentation</p> Signup and view all the answers

    What do routers between VLANs do?

    <p>Filter broadcast traffic, enhance network security, and perform address summarization</p> Signup and view all the answers

    What is the result of using VLANs in a network?

    <p>Improved network management and scalability</p> Signup and view all the answers

    What is the benefit of VLANs in terms of network complexity?

    <p>Reduced complexity</p> Signup and view all the answers

    What is the relationship between VLANs and network devices?

    <p>VLANs can be implemented without requiring multiple sets of cabling and networking devices</p> Signup and view all the answers

    What is the term used to describe a network link carrying multiple VLANs?

    <p>Trunk</p> Signup and view all the answers

    What is the purpose of VLAN tagging?

    <p>To create the appearance and functionality of network traffic that is physically on a single network but acts as if it is split between separate networks</p> Signup and view all the answers

    What is the purpose of inserting labels or tags into packets in a VLAN network?

    <p>To identify the VLAN the packet belongs to</p> Signup and view all the answers

    Why is it necessary for a technician to have administrative access to a device or keep VLAN port assignment charts?

    <p>To view the device's VLAN configuration</p> Signup and view all the answers

    What is the protocol most commonly used today to support VLANs?

    <p>IEEE 802.1Q</p> Signup and view all the answers

    What type of links are trunk links often used between?

    <p>Switch-to-switch</p> Signup and view all the answers

    Why is tagging used when a VLAN port group is extended to another device?

    <p>To identify the VLAN the packet belongs to</p> Signup and view all the answers

    What is the purpose of a router in a VLAN network?

    <p>To route packets between VLANs</p> Signup and view all the answers

    What is the issue with early proprietary VLAN protocols?

    <p>They are vendor-specific</p> Signup and view all the answers

    What is the primary function of Multiple VLAN Registration Protocol (MVRP)?

    <p>To dynamically share VLAN information and configure the needed VLANs</p> Signup and view all the answers

    How can VLAN membership be established?

    <p>Both statically and dynamically</p> Signup and view all the answers

    What is the purpose of a VLAN Management Policy Server (VMPS)?

    <p>To assign switch ports to VLANs dynamically</p> Signup and view all the answers

    What is the relationship between ports and VLANs in a static VLAN assignment?

    <p>A device assumes the VLAN of the port when it connects to the network</p> Signup and view all the answers

    What is the purpose of protocol-based VLANs?

    <p>To segregate traffic based on protocol</p> Signup and view all the answers

    What is the comparable IEEE standard in use by other manufacturers?

    <p>GARP VLAN Registration Protocol (GVRP)</p> Signup and view all the answers

    What is the purpose of Multiple VLAN Registration Protocol (MVRP)?

    <p>To dynamically share VLAN information and configure the needed VLANs</p> Signup and view all the answers

    What is the benefit of using dynamic VLANs?

    <p>It allows for automatic configuration of VLANs based on information such as the source MAC address of the device connected to the port</p> Signup and view all the answers

    What is the command used to verify the VLAN configuration?

    <p>showvlan brief</p> Signup and view all the answers

    What is the status of VLAN 1 in the given configuration?

    <p>active</p> Signup and view all the answers

    What is the purpose of configuring a voice VLAN on ports connected to phones?

    <p>to separate voice and data traffic</p> Signup and view all the answers

    What is the operational mode of the Fa0/4 interface?

    <p>static access</p> Signup and view all the answers

    What is the access mode VLAN of the Fa0/4 interface?

    <p>10</p> Signup and view all the answers

    What is the command used to save the configuration?

    <p>wr</p> Signup and view all the answers

    What layer of the OSI model do VLANs operate on?

    <p>Data link layer</p> Signup and view all the answers

    What was the primary motivation behind Sincoskie's search for alternatives to IP routing?

    <p>To reduce the processing power required per packet</p> Signup and view all the answers

    What is the purpose of the VLAN tag added to each Ethernet frame?

    <p>To enable multitree bridging and improve scalability</p> Signup and view all the answers

    What is the result of using multiple spanning trees in a network?

    <p>Centralized switches becoming bottlenecks</p> Signup and view all the answers

    What is the standard that describes Ethernet VLANs?

    <p>IEEE 802.1Q-1998</p> Signup and view all the answers

    What is the benefit of using VLANs in modern Ethernet networks?

    <p>Improved network scalability and manageability</p> Signup and view all the answers

    What is the purpose of nested VLAN tags in IEEE 802.1ad?

    <p>To enable provider bridging</p> Signup and view all the answers

    What was the original vision for VLANs in modern Ethernet networks?

    <p>To enable multitree bridging and improve scalability</p> Signup and view all the answers

    What is the limitation of using switches to connect multiple Ethernet networks in a fault-tolerant fashion?

    <p>Centralized switches becoming bottlenecks</p> Signup and view all the answers

    What is the status of VLAN 1 in the given configuration?

    <p>active</p> Signup and view all the answers

    Which interfaces are associated with VLAN 11?

    <p>None</p> Signup and view all the answers

    What is the purpose of configuring Voice and Data VLAN on ports connected to phones?

    <p>To separate voice and data traffic for better security</p> Signup and view all the answers

    What is the command to verify the VLAN configuration?

    <p>show vlan brief</p> Signup and view all the answers

    What is the trunking native mode VLAN of the Fa0/4 interface?

    <p>VLAN 1</p> Signup and view all the answers

    What is the operational mode of the Fa0/4 interface?

    <p>static access</p> Signup and view all the answers

    What is the access mode VLAN of the Fa0/4 interface?

    <p>VLAN 10</p> Signup and view all the answers

    What is the voice VLAN of the Fa0/4 interface?

    <p>VLAN 11</p> Signup and view all the answers

    What is the primary reason for segmenting physical LANs?

    <p>To reduce the size of the data link layer broadcast domain</p> Signup and view all the answers

    What is a common practice when configuring VLANs?

    <p>Assigning non-overlapping address ranges to different VLANs</p> Signup and view all the answers

    What is a characteristic of a basic switch that is not configured for VLANs?

    <p>VLAN functionality is enabled by default with a default VLAN that contains all ports</p> Signup and view all the answers

    What is a limitation of using VLANs with overlapping address ranges?

    <p>It is not possible to route data between two networks with overlapping addresses</p> Signup and view all the answers

    What is a requirement for remote management of a switch?

    <p>The administrative functions must be associated with one or more of the configured VLANs</p> Signup and view all the answers

    What is a benefit of using VLANs?

    <p>It restricts access to network resources without regard to physical topology</p> Signup and view all the answers

    What is the relationship between VLANs and IP networks?

    <p>VLANs are assigned to IP networks or subnets</p> Signup and view all the answers

    What is the OSI layer at which VLANs operate?

    <p>Data link layer</p> Signup and view all the answers

    What is the maximum number of VLANs supported by IEEE 802.1Q?

    <p>4,094</p> Signup and view all the answers

    What is the purpose of Cisco's Inter-Switch Link (ISL) protocol?

    <p>To interconnect switches and maintain VLAN information</p> Signup and view all the answers

    What is the main difference between ISL and IEEE 802.1Q tagging?

    <p>ISL uses external tagging, while IEEE 802.1Q uses internal tagging</p> Signup and view all the answers

    What is the purpose of VLAN Trunking Protocol (VTP)?

    <p>To propagate the definition of VLANs on the whole local area network</p> Signup and view all the answers

    What is the extension of IEEE 802.1Q that adds support for multiple, nested VLAN tags?

    <p>IEEE 802.1ad</p> Signup and view all the answers

    Why is ISL proprietary protocol deprecated?

    <p>It has been replaced by IEEE 802.1Q</p> Signup and view all the answers

    What is the limitation of the number of VLANs in IEEE 802.1Q when using the Shortest Path Bridging feature?

    <p>16,000,000</p> Signup and view all the answers

    What is the benefit of using VLANs in terms of network design?

    <p>It allows for a more scalable network design</p> Signup and view all the answers

    What is the term used to describe a network link carrying multiple VLANs?

    <p>Trunk</p> Signup and view all the answers

    What is the primary function of a router in a VLAN setup?

    <p>To route traffic between different VLANs</p> Signup and view all the answers

    What is the protocol commonly used to support VLANs?

    <p>IEEE 802.1Q</p> Signup and view all the answers

    Why is tagging required when extending a VLAN port group to another device?

    <p>Because communications between ports on two different switches travel via the uplink ports of each switch</p> Signup and view all the answers

    What is a limitation of switches in VLAN configuration?

    <p>They have no built-in method to indicate VLAN to port associations</p> Signup and view all the answers

    What is the purpose of keeping VLAN port assignment charts or diagrams near switches in a wiring closet?

    <p>To indicate VLAN to port associations</p> Signup and view all the answers

    Which of the following is a proprietary protocol used to support VLANs?

    <p>Cisco Inter-Switch Link (ISL)</p> Signup and view all the answers

    What is the reason for using tags in VLAN trunks?

    <p>To identify VLANs in a trunk</p> Signup and view all the answers

    Study Notes

    VLANs and Network Management

    • VLANs (Virtual Local Area Networks) help manage broadcast traffic by forming multiple broadcast domains.
    • Breaking up a large network into smaller independent segments reduces the amount of broadcast traffic each network device and network segment has to bear.
    • VLANs can logically group networks to decouple users' network location from their physical location.

    VLANs and IP Subnets

    • VLANs are data link layer (OSI layer 2) constructs, analogous to Internet Protocol (IP) subnets, which are network layer (OSI layer 3) constructs.
    • A one-to-one relationship often exists between VLANs and IP subnets, although it is possible to have multiple subnets on one VLAN.

    Benefits of VLANs

    • VLANs provide flexibility to adapt to changes in network requirements and allow for simplified administration.
    • VLANs can be used to partition a local network into several distinctive segments, such as production, voice over IP, network management, storage area network (SAN), guest Internet access, and demilitarized zone (DMZ).

    VLANs and Security

    • VLANs can provide a measure of security with great flexibility for a comparatively low cost.
    • However, VLANs as a security solution should be implemented with great care as they can be defeated unless implemented carefully.

    VLANs in Cloud Computing

    • In cloud computing, VLANs, IP addresses, and MAC addresses in the cloud are resources that end users can manage.
    • Placing cloud-based virtual machines on VLANs may be preferable to placing them directly on the Internet.

    Network Technologies with VLAN Capabilities

    • Network technologies with VLAN capabilities include Asynchronous Transfer Mode (ATM), Fiber Distributed Data Interface (FDDI), Ethernet, HiperSockets, and InfiniBand.

    VLAN Tagging

    • IEEE 802.1Q and ISL (Inter-Switch Link) are two methods of VLAN tagging.
    • IEEE 802.1Q uses a frame-internal field for tagging, while ISL uses an external tagging process that does not modify the Ethernet frame.

    IEEE 802.1Q

    • Under IEEE 802.1Q, the maximum number of VLANs on a given Ethernet network is 4,094.
    • IEEE 802.1ad extends the number of VLANs supported by adding support for multiple, nested VLAN tags.
    • IEEE 802.1aq (Shortest Path Bridging) expands the VLAN limit to 16 million.
    • ISL is a Cisco proprietary protocol used to interconnect switches and maintain VLAN information as traffic travels between switches on trunk links.
    • ISL is available only on some Cisco equipment and has been deprecated.

    Cisco VLAN Trunking Protocol (VTP)

    • VTP is a Cisco proprietary protocol that propagates the definition of VLANs on the whole local area network.
    • VTP is available on most of the Cisco Catalyst Family products.

    Configuring VLANs

    • VLANs can be configured using the vlan command in Cisco switches.
    • VLANs can be verified using the show vlan brief command.
    • VLANs can be removed using the no vlan command.

    Configuring Voice and Data VLANs

    • Voice and data VLANs can be configured on ports connected to phones using the switchport mode access and switchport voice vlan commands.
    • The switchport access vlan command is used to configure the access VLAN for a port.
    • The switchport voice vlan command is used to configure the voice VLAN for a port.

    VLAN & Configuration

    • A Virtual Local Area Network (VLAN) is a broadcast domain that is partitioned and isolated in a computer network at the data link layer (OSI layer 2).
    • VLANs work by applying tags to network frames and handling these tags in networking systems, creating the appearance and functionality of network traffic that is physically on a single network but acts as if it is split between separate networks.

    VLAN Implementation

    • To subdivide a network into VLANs, one configures network equipment, such as simpler equipment that partitions each physical port or more sophisticated devices that mark frames through VLAN tagging.
    • VLANs share bandwidth, and a VLAN trunk can use link aggregation, quality-of-service prioritization, or both to route data efficiently.
    • VLANs address issues such as scalability, security, and network management, and network architects set up VLANs to provide network segmentation.

    VLAN Benefits

    • VLANs can help manage broadcast traffic by forming multiple broadcast domains, reducing the amount of broadcast traffic each network device and network segment has to bear.
    • VLANs can also help create multiple layer 3 networks on a single physical infrastructure.
    • VLANs provide flexibility to adapt to changes in network requirements and allow for simplified administration.

    VLAN Types and Applications

    • VLANs can be used to partition a local network into several distinctive segments, such as:
      • Production
      • Voice over IP
      • Network management
      • Storage area network (SAN)
      • Guest Internet access
      • Demilitarized zone (DMZ)
    • VLANs can be used in cloud computing to manage virtual machines and mitigate security issues.

    VLAN History

    • Dr. W. David Sincoskie invented VLANs by adding a tag to each Ethernet frame, allowing for the interconnection of multiple Ethernet networks.
    • The IEEE 802.1Q-1998 standard described Ethernet VLANs, and IEEE 802.1ad extended this to allow nested VLAN tags.

    VLAN Configuration

    • VLANs can be configured using commands such as vlan 10 and switchport mode access to set up VLANs on a switch.
    • Verification commands such as show vlan brief and show interface fa0/4 switchport can be used to check VLAN configuration.

    Conclusion

    • VLANs operate at the data link layer of the OSI model, and are used to divide a single broadcast domain into multiple broadcast domains.

    VLAN & Configuration

    Introduction to VLANs

    • VLAN stands for Virtual Local Area Network.
    • VLANs divide a single broadcast domain into multiple broadcast domains.
    • VLANs work by applying tags to network frames and handling these tags in networking systems.

    VLAN Implementation

    • To subdivide a network into VLANs, network equipment is configured.
    • VLAN tagging allows multiple VLANs to be transported over a single interconnect (trunk).
    • VLANs address issues such as scalability, security, and network management.
    • Network architects set up VLANs to provide network segmentation.
    • Routers between VLANs filter broadcast traffic, enhance network security, perform address summarization, and mitigate network congestion.

    VLAN Trunk

    • A VLAN trunk is a network link carrying multiple VLANs, identified by labels (or tags) inserted into their packets.
    • Trunks must run between tagged ports of VLAN-aware devices, often switch-to-switch or switch-to-router links.
    • A router (Layer 3 device) serves as the backbone for network traffic going across different VLANs.

    Protocols and Design

    • The protocol most commonly used to support VLANs is IEEE 802.1Q.
    • IEEE 802.1Q is a method of multiplexing VLANs that provides multivendor VLAN support.
    • Other protocols include Cisco Inter-Switch Link (ISL), 3Com's Virtual LAN Trunk (VLT), and GARP VLAN Registration Protocol (GVRP) or Multiple VLAN Registration Protocol (MVRP).

    VLAN Membership

    • VLAN membership can be established either statically or dynamically.
    • Static VLANs are also referred to as port-based VLANs.
    • Dynamic VLANs are created using software or by protocol.
    • VLAN Management Policy Server (VMPS) allows administrators to assign switch ports to VLANs dynamically based on information such as the source MAC address of the device connected to the port or the username used to log onto that device.

    VLAN Configuration

    • VLAN configuration involves creating a VLAN, naming it, and assigning ports to the VLAN.
    • VLAN configuration can be verified using the show vlan brief command.

    Verifying VLANs

    • The show vlan brief command displays information about VLANs, including VLAN name, status, and ports.
    • The show interface command displays information about a specific interface, including switchport mode, access mode VLAN, and voice VLAN.

    VLANs and their History

    • VLANs were invented by Sincoskie to alleviate the bottleneck problem caused by centrally located switches in a fault-tolerant network.
    • Sincoskie added a tag to each Ethernet frame, which is now known as the IEEE 802.1Q header or VLAN tag.

    VLAN Configuration and Design

    • VLANs operate at the data link layer of the OSI model.
    • VLANs can be used to separate broadcast domains across one physical medium.
    • VLANs can also serve to restrict access to network resources without regard to physical topology.
    • Administrators often configure a VLAN to map directly to an IP network or subnet.
    • VLANs within the same organization will typically be assigned different non-overlapping network address ranges.
    • It is not possible to route data between two networks with overlapping addresses without IP remapping.

    VLAN Trunks and Switch Management

    • A trunk denotes a network link carrying multiple VLANs, which are identified by labels inserted into their packets.
    • Trunks must run between tagged ports of VLAN-aware devices.
    • A router (Layer 3 device) serves as the backbone for network traffic going across different VLANs.
    • Switches typically have no built-in method to indicate VLAN to port associations to someone working in a wiring closet.

    VLAN Protocols and Design

    • The protocol most commonly used to support VLANs is IEEE 802.1Q.
    • IEEE 802.1Q provides multivendor VLAN support.
    • Prior to the introduction of the 802.1Q standard, several proprietary protocols existed, such as Cisco Inter-Switch Link (ISL) and 3Com's Virtual LAN Trunk (VLT).
    • IEEE 802.1Q tagging allows for explicit tagging of frames with VLAN information.

    IEEE 802.1Q and its Limitations

    • Under IEEE 802.1Q, the maximum number of VLANs on a given Ethernet network is 4,094.
    • This does not impose the same limit on the number of IP subnets in such a network since a single VLAN can contain multiple IP subnets.
    • IEEE 802.1ad extends the number of VLANs supported by adding support for multiple, nested VLAN tags.
    • IEEE 802.1aq (Shortest Path Bridging) expands the VLAN limit to 16 million.

    Cisco Proprietary Protocols

    • Inter-Switch Link (ISL) is a Cisco proprietary protocol used to interconnect switches and maintain VLAN information as traffic travels between switches on trunk links.
    • ISL is provided as an alternative to IEEE 802.1Q.
    • VLAN Trunking Protocol (VTP) is a Cisco proprietary protocol that propagates the definition of VLANs on the whole local area network.

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    Related Documents

    ch8.pdf

    Description

    Learn how VLANs can help manage broadcast traffic in a network by forming multiple broadcast domains and reducing the amount of broadcast traffic each network device and segment has to bear.

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