vlan in network

Its stands for Virtual Local Area Network. It is a group of devices on one or more LANs that are configured to communicate as if they are attached to the same network.

Characteristics of VLAN:

• A Virtual Local Area Network (VLAN) is a grouping of network nodes like computers, servers and network devices are connected in a logical form.
• It increases the broadcast domains.
• It is providing layer 2 security.
• It will happen in Data Link layer of OSI model.
• VLAN 1 is the default VLAN.
• It can be configured only manageable switch.
• It is divided a larger broadcast domain into multiple smaller broadcast domains.
• It allows the network administrator to grouping by hosts even if the hosts are not directly connected to the same network switch.
• It is easy to change and manage users on a VLAN.

Advantages of VLAN:

• It provides solution of broadcast problem.
• It is reduced the size of broadcast domains.
• It provides additional layer of security.
• It is easily managed and add users.
• Its infrastructure is much cheaper because it’s not required hardware and cable.

Disadvantages of VLAN:

• It cannot provide the data to the other VLANs.
• If attacking a one system, it effected the whole logical network.

Benefit of VLAN:

• Broadcast Control:

When VLAN is created in Switch the number is broadcast domain increases but the size of broadcast domain decreases.

• Security:

VLAN increases layer – 3 security. Only the member of a broadcast domain can have access to the network resources in that particular group. Using VLAN we can restrict hardware address protocol and application.

• Flexibility & Scalability:

Using VLAN devices can be added or remove very easily. A group of users that need a different group for security purpose can be added to a different VLAN, so that other users cannot access them.

Types of VLAN:

There are 5 types of VLANs depending their network traffic –

1. Default VLAN:

When switch start all switch, port become a member of the default VLAN. It makes them a member of a particular broadcast domain. So that they can communicate. In Cisco switches default VLAN is VLAN 1.

2. Data VLAN: –

This VLAN is used to carry only user traffic. It will not carry any management and control related information.

3. Native VLAN: –

A Native VLAN is assigned to an 802.1Q Trunk port. It supports traffic coming many VLAN as well as other Trunk port.

4. Management VLAN: –

This type of VLAN is configure to access the management capability of a Switch.

5. Voice VLAN: –

This VLAN is configure to carry voice traffic. This traffic has the greater priority than data.

VLAN Membership:

There are 2 types of VLAN Membership –

Static VLAN:

• Static VLANs are typically method of creating VLANs by Administrator.
• It is based on Port number.
• It is manually assigning by the administrator on a switch to particular port for the particular VLAN.
• It is also called a Port-based VLAN Membership.
• Here single port can be member of single VLAN.

Dynamic VLAN:

• Dynamic VLAN are created using software or based on the MAC address.
• Here, Switch automatically assigning the port to a VLAN.
• Each port can be member of Multiple VLAN.
• For Dynamic VLAN configuration required VMPS (VLAN Membership Policy Server).

Types of VLAN Port:

1. Access Port:

• It is a member of particular a VLAN.
• It carries traffic of only one VLAN.
• Traffic is both sent & received in native format with no VLAN information.
• Any traffic received in a part is consider that it belongs to the same VLAN.
• Any device that is attached to an access port don’t know which VLAN it is connected to.
• When data is sent through an access port the VLAN information is remove.

2. Trunk Port:

• This name is taken from Telephone system Trunk which carry multiple telephone conversion at a time.
• Trunk port can carry traffic of multiple VLAN.
• A Trunk port must have 100 Mbps, 1 Gbps, 10 Gbps speed.
• It is a point-to-point connection between two switches, a switch and a router, a switch and a server.

VLAN Trunking Protocols:

There are 2 protocols are commonly used in VLAN –

ISL (Inter-Switch Link):

It is a Cisco proprietary protocol.
It is used to interconnect switches and it maintain VLAN information.
It uses an internal process tagging that does not modify ethernet frame.

802.1Q:

It is also known as Dot1q.
It is an IEEE standard protocol.
It is an open standard protocol.
It is uses frame-internal process for tagging that modify the ethernet frame.
It is supported upto 4094 VLANs.

VLAN Interview Questions

Q #. What is VLAN?
Ans: – A VLAN or Virtual Local Area Network is a group of devices that are used to be a single broadcast domain divided into multiple broadcast domains in layer 2 switch network.

Q #. How to create VLAN?
Ans: –
Switch(config)# vlan 50
Switch(config-vlan)# name networkhelp
Switch(config-vlan)# exit

Q #. How to add an interface to a VLAN?
Ans: –
Switch(config)# interface fastethernet 0/0
Switch(config-vlan)# switchport mode access
Switch(config-vlan)# switchport access vlan 30
Switch(config-vlan)# exit

Q #. How to add multiple interface in VLAN at a time?
Ans: –
Switch(config)# interface range fastethernet 0/1 – 2
Switch(config-vlan)# switchport mode access
Switch(config-vlan)# switchport access vlan 200
Switch(config-vlan)# exit

Q #. How to change native VLAN?
Ans: –
Switch(config)# interface fastethernet 0/0
Switch(config-if)# switchport trunk native vlan 100

Q #. Which command is used to see trunk interfaces?
Ans: –
Switch# show interface trunk

Q #. Which command is used to see all VLAN information?
Ans: –
Switch# show vlan

Q #. What is the comment of delete vlan information from Switch?
Ans: – Delete flash:vlan.dat

Q #. What is the difference between VLAN Access and Trunk Mode?
Ans: – Access Mode is used to connect end device (host) to switch while Trunk Mode is used to connect between switches.

Q #. What is mean by “Router on Stick”?
Ans: – The process of connecting one physical (ethernet) link with the trunk logical interface and their configuration as 802.1q link, is called as “Router-on-Stick”. Here, switch is connected within multiple VLAN and router works routing in every VLAN.

Q #. Name of the Trunking Protocols?
Ans: –
• ISL (Inter Switch Link) – This is a Cisco proprietary protocol.
• 802.1q – This is an IEEE standard protocol.

Q #. What is the maximum number of vlans allowed in ISL and 802.1Q?
Ans: –
• ISL maximum permitted in vlan – 1000.
• 802.1Q maximum permitted in vlan – 4094.

Q #. What is the name of VLAN that not tagged by 802.1Q?
Ans: – Native VLAN.

VLAN Range

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VLAN in Network:

What is VLAN (Virtual LAN)?