w6ch5

Podcast Beta

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the primary goal of the IEEE 802.1 working group's VLAN multiplexing method?

To provide multivendor VLAN support (correct)

To introduce proprietary protocols like ISL

To limit the number of VLANs on a network

To replace Ethernet hardware with new standards

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

ISL uses an external tagging process, while 802.1Q uses a frame-internal field (correct)

ISL is proprietary, while 802.1Q is open standard

ISL modifies the Ethernet frame, while 802.1Q does not

ISL is faster, while 802.1Q is slower

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

Unlimited

16 million

4,094 (correct)

4,096

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

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

What is the comparable IEEE standard to VTP?

GARP VLAN Registration Protocol (GVRP) Signup and view all the answers

What is an advantage of IEEE 802.1Q over ISL?

IEEE 802.1Q works on both access and trunk links using standard Ethernet hardware Signup and view all the answers

What is the purpose of IEEE 802.1ad?

To extend the number of VLANs supported by adding support for multiple, nested VLAN tags Signup and view all the answers

What is the current status of ISL protocol?

It has been deprecated Signup and view all the answers

What is the name of the ports that are used to pass traffic from multiple VLANs?

Trunk ports Signup and view all the answers

What is the purpose of adding identification tags to frames in a trunk port?

To distinguish between frames from different VLANs Signup and view all the answers

What happens to untagged frames when they reach a trunk end?

They are tagged to ensure correct forwarding Signup and view all the answers

What is VLAN Encapsulation?

A process of adding tags to frames for identification Signup and view all the answers

Which type of traffic will not cross VLAN boundaries?

Layer 2 unicast, multicast, and broadcast Signup and view all the answers

What type of tags are added to frames by switches with trunk ports?

Either 802.1Q tags or Inter-Switch Link (ISL) tags Signup and view all the answers

What is the purpose of a trunk link?

To carry traffic from multiple VLANs between switches Signup and view all the answers

What happens to tagged frames when they reach the receiving switch?

They are decapsulated to check the destination VLAN Signup and view all the answers

What is the primary function of the Tag Protocol ID (TPID) in an IEEE 802.1q frame?

To identify the frame as an IEEE 802.1q frame Signup and view all the answers

What is the maximum number of unique VLANs that can be supported on a single Ethernet network using 802.1q encapsulation?

4096 Signup and view all the answers

What is the purpose of the Canonical Format Indicator (CFI) field in an IEEE 802.1q frame?

To indicate Drop Eligibility Signup and view all the answers

What is the length of the VLAN tag in an IEEE 802.1q frame?

4 bytes Signup and view all the answers

What is the purpose of VLAN cross connect (CC or VLAN-XC) mechanism?

To create Switched VLANs Signup and view all the answers

What is the standard that specifies the characteristics of physical layer and Media Access Control (MAC) layer for wired Ethernet connections?

IEEE 802.3 Signup and view all the answers

What is the purpose of recalculating the Frame Check Sequence (FCS) in 802.1q encapsulation?

To ensure frame integrity Signup and view all the answers

What is the purpose of the Priority (PRI) field in an IEEE 802.1q frame?

To indicate frame priority level Signup and view all the answers

What is the primary purpose of STP in a network?

To prevent switching loops in the network Signup and view all the answers

What is the IEEE standard for STP protocol?

IEEE 802.1D Signup and view all the answers

What is the effect of redundancy in a network without STP?

It may cause broadcast traffic to loop in the network Signup and view all the answers

What is the purpose of Spanning Trees in STP?

To search for redundant links in the LAN and select the best paths Signup and view all the answers

What is the effect of enabling STP on switch interfaces?

It prevents switching loops in the network Signup and view all the answers

What is the purpose of QinQ in a Broadband Network?

To implement VLAN in the network Signup and view all the answers

What is the limitation of Spanning Tree?

It does not use multiple links to the same destination Signup and view all the answers

What is the necessity of using VLAN, QinQ, and STP together?

To ensure QoS parameters and their optimum values Signup and view all the answers

What is the primary purpose of VLANs in a network?

To improve network scalability and management Signup and view all the answers

How do VLANs manage broadcast traffic?

By forming multiple broadcast domains Signup and view all the answers

What is the relationship between VLANs and IP subnets?

A one-to-one relationship often exists, but it's not always the case Signup and view all the answers

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

The amount of broadcast traffic decreases Signup and view all the answers

What is the main reason why switches do not bridge network traffic between VLANs?

To enhance network security Signup and view all the answers

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

They enable the creation of multiple layer 3 networks on a single physical infrastructure Signup and view all the answers

What happens when the number of peers on a network grows?

The frequency of broadcasts increases Signup and view all the answers

What is a limitation of networks without VLAN capability?

Users are limited by physical topologies and distances Signup and view all the answers

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

To improve network scalability and security Signup and view all the answers

How do VLANs manage broadcast traffic?

By forming multiple broadcast domains Signup and view all the answers

What is the relationship between VLANs and IP subnets?

VLANs are data link layer constructs, while IP subnets are network layer constructs Signup and view all the answers

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

The frequency of broadcasts decreases Signup and view all the answers

Why do switches not bridge network traffic between VLANs?

Because it would violate the integrity of the VLAN broadcast domain Signup and view all the answers

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

It allows for multiple layer 3 networks on a single physical infrastructure Signup and view all the answers

What happens when the number of peers on a network grows?

The frequency of broadcasts increases Signup and view all the answers

What is a limitation of networks without VLAN capability?

They are limited by physical topologies and distances Signup and view all the answers

What is the primary function of STP in a network?

To prevent switching loops Signup and view all the answers

What is the purpose of Spanning Trees in STP?

To select the best paths and put all links in either forwarding or blocking state Signup and view all the answers

What is the effect of enabling STP on switch interfaces?

It prevents switching loops Signup and view all the answers

What is the necessity of using VLAN, QinQ, and STP together?

To ensure QoS parameters and their optimum values Signup and view all the answers

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

To simplify network design and deployment Signup and view all the answers

What can VLANs be used to separate based on?

Individual users or groups of users or their roles Signup and view all the answers

What is the limitation of Spanning Tree?

It cannot load-balance traffic Signup and view all the answers

What is the result of grouping hosts together using VLANs?

Network design and deployment are simplified Signup and view all the answers

What is the purpose of QinQ in a Broadband Network?

To support multiple VLANs Signup and view all the answers

What do VLANs allow devices to do?

Share the cabling of a physical network and be prevented from directly interacting with one another Signup and view all the answers

What is the effect of redundancy in a network without STP?

It creates switching loops Signup and view all the answers

Why is switching necessary in data network?

To support a large number of users Signup and view all the answers

What is a potential security risk when using VLANs?

Traffic escaping from a given VLAN Signup and view all the answers

How do VLANs improve network security?

By keeping network applications separate Signup and view all the answers

What is a common use of VLANs in Internet hosting services?

To separate customers' private zones from one another Signup and view all the answers

What is a result of using VLANs in a network?

Simplified network design and deployment Signup and view all the answers

What is the typical VLAN identifier used by the default VLAN?

1 Signup and view all the answers

What type of device serves as the backbone for network traffic going across different VLANs?

Router Signup and view all the answers

What is necessary for a technician to determine VLAN to port associations?

All of the above Signup and view all the answers

What type of link carries multiple VLANs, identified by labels or tags inserted into their packets?

Trunk link Signup and view all the answers

What is the term used to describe separating ports by VLAN groups?

VLAN separation Signup and view all the answers

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

IEEE 802.1Q Signup and view all the answers

What happens when communications occur between ports on two different switches?

Traffic is tagged Signup and view all the answers

What is the benefit of using VLANs in a network?

It reduces network infrastructure Signup and view all the answers

What is the main function of digital switches in a telephone exchange?

To manage digital signals and forward them to the back-end network Signup and view all the answers

What type of switches do not have an interface for configuration purposes?

Unmanaged switches Signup and view all the answers

What is a common method used to manage a managed switch?

Using a web interface Signup and view all the answers

What is a virtual LAN (VLAN)?

A broadcast domain that is partitioned and isolated at the data link layer Signup and view all the answers

What is the main difference between unmanaged switches and managed switches?

Managed switches have more features than unmanaged switches Signup and view all the answers

What is an example of a configuration change that can be made on a managed switch?

Enabling features such as Spanning Tree Protocol Signup and view all the answers

What is a benefit of using managed switches in a network?

They offer more features and configuration options Signup and view all the answers

What is the purpose of digital switches in a telephone company's back-end network?

To forward digital signals to the telephone company's back-end network Signup and view all the answers

What is the main advantage of using VLANs in a network?

To simplify network design and deployment Signup and view all the answers

What is the primary function of VLANs in a network?

To separate network applications Signup and view all the answers

How do VLANs manage network traffic?

By separating traffic based on individual users or groups Signup and view all the answers

What is the purpose of configuring network equipment to subdivide a network into VLANs?

To partition each physical port Signup and view all the answers

What is the primary purpose of STP in a network?

To prevent switching loops in the network Signup and view all the answers

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

Simplified network design and deployment Signup and view all the answers

What is the standard that governs the STP protocol?

IEEE 802.1D Signup and view all the answers

What can happen if precautions are not taken to prevent traffic 'escaping' from a given VLAN?

VLAN hopping Signup and view all the answers

What happens to redundant links in a network with STP enabled?

They are put in a blocking state Signup and view all the answers

What is the purpose of grouping hosts together using VLANs?

To separate network applications Signup and view all the answers

What is the limitation of Spanning Tree?

It does not support multiple links to the same destination Signup and view all the answers

What is the effect of using VLANs on network management?

Simplified network design and deployment Signup and view all the answers

What is the primary purpose of QinQ in a Broadband Network?

To provide QoS parameters and their optimum values Signup and view all the answers

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

Network size decreases Signup and view all the answers

Why are VLANs, QinQ, and STP used together?

To ensure QoS parameters and their optimum values Signup and view all the answers

What is the effect of redundancy in a network without STP?

Broadcast traffic may get stuck in a loop Signup and view all the answers

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

To improve network scalability and security Signup and view all the answers

Why do routers between VLANs filter broadcast traffic?

To enhance network security Signup and view all the answers

What is the result of breaking up a large network into smaller independent segments using VLANs?

Reduced amount of broadcast traffic each network device has to bear Signup and view all the answers

What is the purpose of VLANs in terms of network segmentation?

To provide network segmentation Signup and view all the answers

What is the primary purpose of QinQ in Metro Ethernet network topologies?

To provide separate instances of MAC services to multiple independent users Signup and view all the answers

What is the relationship between VLANs and IP subnets?

A one-to-one relationship often exists between VLANs and IP subnets Signup and view all the answers

What is the formal name of the QinQ protocol?

IEEE 802.1ad Signup and view all the answers

What happens when the number of peers on a network grows?

The frequency of broadcasts increases Signup and view all the answers

What is a limitation of networks without VLAN capability?

Users are limited by physical topologies and distances Signup and view all the answers

What is the purpose of the outer VLAN tag in a QinQ frame?

To identify the end user uniquely Signup and view all the answers

What is the term used to describe the multiple VLAN headers in a QinQ frame?

Tag stack Signup and view all the answers

Why do switches not bridge network traffic between VLANs?

Because doing so would violate the integrity of the VLAN broadcast domain Signup and view all the answers

What is the advantage of using QinQ in a Broadband Network?

It enables the identification of end users and segregation of traffic Signup and view all the answers

What is the result of implementing QinQ in a network?

It provides separate instances of MAC services to multiple independent users Signup and view all the answers

What is the purpose of the inner VLAN tag in a QinQ frame?

To provide a separate instance of MAC services Signup and view all the answers

What is the primary purpose of the VLAN ID field in an IEEE 802.1q frame?

To identify which VLAN the current frame belongs to Signup and view all the answers

What is the length of the VLAN tag in an IEEE 802.1q frame?

4 bytes Signup and view all the answers

What is the benefit of using QinQ in a Metro Ethernet network?

It enables the provision of separate instances of MAC services to multiple independent users Signup and view all the answers

What is the purpose of recalculating the Frame Check Sequence (FCS) in 802.1q encapsulation?

To accommodate the additional VLAN tag in the Ethernet frame Signup and view all the answers

What is the purpose of the Priority (PRI) field in an IEEE 802.1q frame?

To indicate the frame priority level Signup and view all the answers

What is the advantage of using VLAN cross connect (CC or VLAN-XC) mechanism?

It creates Switched VLANs using IEEE 802.1ad frames Signup and view all the answers

What is the standard that specifies the characteristics of physical layer and Media Access Control (MAC) layer for wired Ethernet connections?

IEEE 802.3 Signup and view all the answers

What is the primary purpose of the Tag Protocol ID (TPID) field in an IEEE 802.1q frame?

To identify the frame as an IEEE 802.1q frame Signup and view all the answers

What is the limitation of using 802.1q encapsulation?

It supports only a single VLAN header Signup and view all the answers

What is the primary function of VLANs in a network?

To provide network segmentation and improve security Signup and view all the answers

What is the result of breaking up a large network into smaller independent segments using VLANs?

Reduced broadcast traffic on each network segment Signup and view all the answers

How do VLANs manage broadcast traffic?

By forming multiple broadcast domains Signup and view all the answers

What is the relationship between VLANs and IP subnets?

There is often a one-to-one relationship between VLANs and IP subnets Signup and view all the answers

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

To decouple users' network location from their physical location Signup and view all the answers

What happens when the number of peers on a network grows?

The frequency of broadcasts increases Signup and view all the answers

What is a common infrastructure shared across VLAN trunks used for?

To optimize traffic on trunk links for real-time or low-latency requirements Signup and view all the answers

What is a limitation of networks without VLAN capability?

Users are assigned to networks based on geography and are limited by physical topologies and distances Signup and view all the answers

Why do switches not bridge network traffic between VLANs?

Because doing so would violate the integrity of the VLAN broadcast domain Signup and view all the answers

Why are VLANs invented?

To alleviate the problem of centrally located switches becoming bottlenecks Signup and view all the answers

What is a benefit of placing cloud-based virtual machines on VLANs?

To help mitigate security issues Signup and view all the answers

What is a benefit of VLANs in terms of network infrastructure?

Improved network flexibility and reduced physical topology limitations Signup and view all the answers

What is a limitation of networks without VLAN capability?

Scalability Signup and view all the answers

What is a common use of VLANs in cloud computing?

To manage IP addresses, MAC addresses, and network infrastructure Signup and view all the answers

What is a characteristic of VLANs in terms of network requirements?

Flexibility in adapting to changes Signup and view all the answers

What is a type of network technology that supports VLANs?

Ethernet Signup and view all the answers

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

To manage the flow of data across a network Signup and view all the answers

What is the difference between a hub and a switch?

A hub simply retransmits packets, while a switch distinguishes recipients Signup and view all the answers

What is the benefit of using segmentation in a network?

To split a larger collision domain into smaller ones Signup and view all the answers

What is the role of switches in most modern Ethernet local area networks (LANs)?

To play a vital role in managing data flow Signup and view all the answers

What is the purpose of a switch in a small office/home office (SOHO) application?

To access small office/home broadband services Signup and view all the answers

What is the advantage of using a switch over a hub in a network?

A switch is able to distinguish different recipients Signup and view all the answers

What is the purpose of using multiple linked managed switches in a mid-to-large sized LAN?

To manage data flow across a large network Signup and view all the answers

What is the role of a switch in managing data flow across a network?

To transmit data frames only to the intended recipients Signup and view all the answers

What is the primary method of assigning VLAN membership in a static VLAN?

By assigning ports to a VLAN Signup and view all the answers

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

To assign switch ports to VLANs dynamically Signup and view all the answers

What is the purpose of protocol-based VLANs?

To segregate traffic based on protocol Signup and view all the answers

What is the primary characteristic of a native port?

It accepts traffic from a single VLAN Signup and view all the answers

What is the primary difference between a tagged port and a native port?

A tagged port accepts traffic from multiple VLANs, while a native port accepts traffic from a single VLAN Signup and view all the answers

What is the primary advantage of using dynamic VLANs?

It allows for easier management of VLAN membership Signup and view all the answers

What is the primary purpose of Multiple VLAN Registration Protocol (MVRP) in a dynamic VLAN?

To register VLAN membership dynamically Signup and view all the answers

What is the primary limitation of static VLANs?

It does not allow for dynamic assignment of VLAN membership Signup and view all the answers

What is the main characteristic of untagged ports?

They are involved in exchanging traffic with a single end device Signup and view all the answers

What happens when untagged frames reach a trunk end?

They are tagged to ensure correct forwarding Signup and view all the answers

What is the purpose of VLAN Encapsulation?

To add identification tags to frames for correct forwarding Signup and view all the answers

What is the primary function of a trunk link?

To carry traffic from multiple VLANs Signup and view all the answers

What type of traffic is isolated by VLANs?

Layer 2 unicast, multicast, and broadcast traffic Signup and view all the answers

What is the primary function of a switch with a trunk port?

To add identification tags to frames for correct forwarding Signup and view all the answers

What happens when a switch receives a tagged frame?

It decapsulates the frame to check which VLAN it is destined for Signup and view all the answers

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

To break up a network into smaller independent segments Signup and view all the answers

Study Notes

VLAN Fundamentals

VLANs (Virtual Local Area Networks) allow multiple VLANs to share bandwidth on a single interconnect (trunk) using VLAN tagging.
VLAN trunks can use link aggregation, quality-of-service prioritization, or both to route data efficiently.
VLANs address issues such as scalability, security, and network management by providing network segmentation.

Benefits of VLANs

VLANs 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 create multiple layer 3 networks on a single physical infrastructure.
VLANs are data link layer (OSI layer 2) constructs, analogous to Internet Protocol (IP) subnets, which are network layer (OSI layer 3) constructs.

VLAN Tagging

IEEE 802.1Q tagging performs explicit tagging, tagging the frame itself with VLAN information.
IEEE 802.1Q uses a frame-internal field for tagging, allowing it to work on both access and trunk links using standard Ethernet hardware.
The maximum number of VLANs on a given Ethernet network is 4,094 (4,096 values provided by the 12-bit VID field minus reserved values at each end of the range, 0 and 4,095).

VLAN Trunking Protocols

Cisco 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.
VLAN Trunking Protocol (VTP) is a Cisco proprietary protocol that propagates the definition of VLANs on the whole local area network.
GARP VLAN Registration Protocol (GVRP) or Multiple VLAN Registration Protocol (MVRP) are comparable IEEE standards used by other manufacturers.

VLAN Ports

Untagged ports (also referred to as access ports) do not need to accommodate an additional identification tag as they are involved in exchanging traffic with a single end device.
Tagged ports (also referred to as trunk ports) add identification tags to the frames to distinguish between frames from different VLANs.

VLAN Encapsulation

VLAN Encapsulation is a process where switches add tags to the frames for identification before forwarding them on the trunk.
IEEE802.1Q, also referred to as DOT1Q or 1Q, is the networking standard that supports virtual LANs (VLANs) on an IEEE 802.3 Ethernet network.

IEEE 802.1Q Frame Format

The dot1Q frame standard accommodates a VLAN tag in the original Ethernet frame.
The VLAN tag is 4 bytes long and consists of:
- Tag Protocol ID (TPID): identifies the frame as IEEE 802.1q frame.
- Priority (PRI): indicates frame priority level.
- Canonical Format Indicator (CFI): now known as Drop Eligibility Indicator (DEI), used to indicate frames that can be dropped during congestion.
- VLAN ID: unique for each VLAN, helps in identifying which VLAN the current frame belongs to.

QinQ

QinQ is a mechanism that allows a single Virtual Local Area Network (VLAN) header to be inserted into an Ethernet frame.
VLAN cross connect (CC or VLAN-XC) uses IEEE 802.1ad frames where the S Tag is used as a Label as in MPLS.

STP

STP (Spanning Tree Protocol) is a protocol designed to support redundant links by preventing switching loops in the network.
STP is a Layer 2 protocol used for link management that runs on bridges and switches.
STP protocols are standardized as IEEE 802.1D by IEEE.
Spanning trees use an algorithm to search for the redundant links in the LAN and select the best paths.
STP puts all links in either forwarding or blocking states, with redundant links being in the blocking state.

Digital Switching

Digital switches manage digital signals in a telephone exchange and forward them to the telephone company's back-end network.
They are faster in performance compared to analog switches.

Types of Switches

Unmanaged switches:
- Have no interface for configuration.
- Are plug and play.
- Typically the least expensive switches, often used in small office/home office environments.
- Can be desktop or rack mounted.
Managed/Manageable switches:
- Have one or more methods to modify the operation of the switch.
- Common management methods include: CLI, telnet, Secure Shell, embedded SNMP agent, or web interface.
- Examples of configuration changes include: enabling features like Spanning Tree Protocol, setting port bandwidth, creating/modifying VLANs, etc.

VLAN (Virtual LAN)

A VLAN is a broadcast domain 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.
They can keep network applications separate despite being connected to the same physical network, without requiring multiple sets of cabling and networking devices.
VLANs allow network administrators to group hosts together even if they are not directly connected to the same network switch.
They can simplify network design and deployment, and provide gains in simplicity, security, traffic management, and economy.

VLAN Benefits

Allow devices that must be kept separate to share the cabling of a physical network and yet be prevented from directly interacting with one another.
Can be used to separate traffic within a business based on individual users or groups of users, their roles, or traffic characteristics.
Are used by Internet hosting services to separate customers' private zones from one another.

VLAN Security

VLANs can help manage broadcast traffic by forming multiple broadcast domains.
Routers between VLANs filter broadcast traffic, enhance network security, perform address summarization, and mitigate network congestion.
VLANs can help create multiple layer 3 networks on a single physical infrastructure.

VLAN Trunks

A VLAN trunk is a network link carrying multiple VLANs, identified by labels (or tags) inserted into their packets.
Such trunks must run between tagged ports of VLAN-aware devices, often switch-to-switch or switch-to-router links rather than links to hosts.

Protocols and Design

The protocol most commonly used to support VLANs is IEEE 802.1Q.

STP (Spanning Tree Protocol)

STP is a protocol designed to support redundant links by preventing switching loops in the network.
It is a Layer 2 protocol used for link management that runs on bridges and switches.
STP protocols are standardized as IEEE 802.1D by IEEE.
Redundancy in a network is required to increase its reliability, but it may adversely affect the network when switches flood traffic out all ports.
STP uses an algorithm to search for redundant links in the LAN and select the best paths.
It is mainly used to put all links in either forwarding or blocking states.
Spanning Tree never uses multiple links to the same destination, and there is no load-sharing feature with Spanning Tree.

VLANs (Virtual Local Area Networks)

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.
VLANs can keep network applications separate despite being connected to the same physical network, without requiring multiple sets of cabling and networking devices to be deployed.
VLAN membership can be configured through software, greatly simplifying network design and deployment.
VLANs allow devices that must be kept separate to share the cabling of a physical network and yet be prevented from directly interacting with one another.
VLANs can be used to separate traffic within a business based on individual users or groups of users or their roles, or based on traffic characteristics.

Benefits of VLANs

Simplify network design and deployment
Increase security
Improve traffic management
Enhance economy
Group hosts together even if they are not directly connected to the same network switch

VLAN Configuration and Security

VLANs share bandwidth, and a VLAN trunk can use link aggregation, quality-of-service prioritization, or both to route data efficiently.
Precautions are needed to prevent traffic "escaping" from a given VLAN, an exploit known as VLAN hopping.
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 Tags and Frames

IEEE802.1Q, often referred to as DOT1Q or 1Q, is the networking standard that supports virtual LANs (VLANs) on an IEEE 802.3 Ethernet network.
The dot1Q frame standard accommodates a VLAN tag in the original Ethernet frame, which is 4 bytes long and consists of the fields:
- Tag Protocol ID (TPID): 0x8100
- Priority (PRI): frame priority level
- Canonical Format Indicator (CFI): Drop Eligibility Indicator (DEI)
- VLAN ID: unique for each VLAN, 12 bits long, supporting 2^12 (4096) unique VLANs on a single Ethernet network

QinQ ( IEEE 802.1ad)

QinQ allows multiple VLAN tags to be inserted into a single frame, essential for implementing Metro Ethernet network topologies.
QinQ extends 802.1Q and is extended by other Metro Ethernet protocols.
A QinQ frame is a frame that has 2 VLAN 802.1Q headers (double-tagged).
QinQ is used in broadband networks to identify the end user uniquely and segregate the users' traffic using an outer VLAN and inner VLAN tag.

STP (Spanning Tree Protocol)

STP is a protocol that prevents switching loops in the network by supporting redundant links.
STP is a Layer 2 protocol used for link management that runs on bridges and switches.
STP protocols are standardized as IEEE 802.1D by IEEE.
Redundancy in networks is required to increase reliability, but STP prevents broadcast traffic from looping in the network.
Spanning trees use an algorithm to search for the redundant links in the LAN and select the best paths.
Spanning Tree never uses multiple links to the same destination and does not have a load-sharing feature.

Switching

Switching plays a vital role in modern Ethernet local area networks (LANs), managing the flow of data across a network by transmitting received data frames only to the intended devices.
A switch is a device that connects other devices together, allowing communication between different networked devices.
Switches operate at the data link layer (layer 2) and create separate collision domains for each switch port, improving overall network throughput.

VLANs

VLANs (Virtual Local Area Networks) address issues such as scalability, security, and network management.
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 logically group networks to decouple the users' network location from their physical location, allowing for simplified administration.
VLANs can provide a measure of security with great flexibility and a relatively low cost, but they can be defeated if not implemented carefully.

VLAN Membership

VLAN membership can be established either statically or dynamically.
Static VLANs are also referred to as port-based VLANs, where ports are assigned to a VLAN.
Dynamic VLANs are created using software or by protocol, such as a VLAN Management Policy Server (VMPS).

VLAN Enabled Ports

VLAN enabled ports can be categorized into two types:
- Untagged or Native ports: accept traffic from a single VLAN and are used to link end devices like routers, servers, and terminals.
- Tagged or Trunk ports: used to pass traffic from multiple VLANs and are used to link switches, adding identification tags to the frames to distinguish between VLANs.

VLAN Tagging

VLAN tagging is a process where switches add identification tags to the frames for identification, allowing the switch on the other side of the trunk to forward the frames to the right destinations.
VLAN tagging is also known as VLAN Encapsulation.

QinQ and STP

QinQ (802.1Q-in-Q) is a technique used to add a second VLAN tag to a frame, allowing for multiple VLANs to be carried over a single link.
Spanning Tree Protocol (STP) is used to prevent network loops and improve network reliability, ensuring that there is only one active path from any source node to any destination on the network.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

Learn about VLANs, their benefits, and how they improve network scalability, security, and management by providing network segmentation.