What is VLAN?
A Virtual Local Area Network (VLAN) is a network technology used to divide a single physical network into multiple logical networks.
This division is achieved at the data link layer (Layer 2) of the OSI model. VLANs are widely used in enterprise networks for their ability to improve network efficiency, security, and manageability.
Key Concepts / How VLANs Work
Logical Segmentation: VLANs segregate network traffic logically, even though the traffic might be transiting the same physical network infrastructure. This segmentation helps in reducing broadcast domains, thereby improving network performance.
Identification: VLANs are typically identified by a VLAN ID, a unique number assigned to each VLAN.
Tagging: VLANs use a process known as tagging to identify and keep track of data packets on the network. The most common tagging method is IEEE 802.1Q. It adds a VLAN tag in the Ethernet frame, specifying the VLAN to which the packet belongs.
Trunk Links: In networks with VLANs, trunk links are used to carry traffic from multiple VLANs across network devices like switches and routers. These links are capable of handling traffic from all VLANs.
Types of VLANs
Data VLAN: Used for user-generated traffic.
Voice VLAN: Specialized for VoIP (Voice over IP) traffic.
Management VLAN: Used for managing network equipment.
Native VLAN: The default VLAN for a port, used in Trunk ports.
Configuration
VLANs are configured on network switches and routers. Each port on a managed switch can be assigned to a specific VLAN.
Ports can be configured as ‘access’ (for end devices, carrying traffic for a single VLAN) or ‘trunk’ (for connections between switches, carrying traffic for multiple VLANs).
On this page, we learn how to configure:
* Telnet line and Password
* Console line and Password
* VLAN and names
* Switch host names
* Delete a VLAN
* Assigning a switch port
The following is a basic configuration of VLAN on Cisco Switch Interfaces:
Before you begin you must have worked out your IP addresses
We are configuring VLAN ports for three departments:
VLAN 10, Name: orbit
VLAN 20, Name:cisco
VLAN 30, Name: Student
We use the topology below as an example:
Configuring Telnet line and password:
switch1#config t
Switch1(config)#enable secret cisco
Switch1(config)#line vty 0 15
Switch1(config-line)#password cisco
Switch1(config-line)#login
Switch1(config-line)#exit
Configuring console line and password:
Switch1(config)#line con 0
Switch1(config-line)#password cisco
Switch1(config-line)#login
Switch1(config-line)#exit
Create and Configure VLANs and Names on Switch:
Switch1#config t
switch1(config)#vlan 10
switch1(config-vlan)#name orbit
switch1(config-vlan)#exit
switch1(config)#vlan 20
switch1(config-vlan)#name cisco
Switch11(config-vlan)#exit
Switch1(config)#vlan 30
Switch1(config-vlan)#name student
Switch1(config-vlan)#exit
Switch1(config)#exit
To view your configurations, use the show vlan command: –
Switch1#show vlan
VLAN Name Status Ports
—- ——————————– ——— ——————————-
1 default active Fa0/1, Fa0/2, Fa0/3, Fa0/4
Fa0/5, Fa0/6, Fa0/7, Fa0/8
Fa0/9, Fa0/10, Fa0/11, Fa0/12
Fa0/13, Fa0/14, Fa0/15, Fa0/16
Fa0/17, Fa0/18, Fa0/19, Fa0/20
Fa0/21, Fa0/22, Fa0/23, Fa0/24
Gig1/1, Gig1/2
10 orbit active
20 cisco active
30 student active
1002 fddi-default active
1003 token-ring-default active
1004 fddinet-default active
005 trnet-default active
<input omitted>
Switch#
How to assign a switchport to a VLAN.
After creating your VLAN, you can assign a switch port to the VLAN . VLAN 20, is statically assigned to port F0/8 on switch S1:
Switch1#config t
Switch1(config)#interface fa0/2
Switch1(config-if)#switchport mode access
Switch1(config-if)#switchport access vlan 20
Switch1(config-if)#no shut
Switch1(config-if)#exit
Switch1(config)#exit
Switch1#
you can use the above commands to assign the rest of the VLANs a switchport access.
How to delete VLANs
To delete a VLAN, use the global configuration command no vlan vlan-id to remove VLAN 20 from the switch.
e.g.
Switch1(config)#no vlan 10
Switch1(config)#end
Use the show vlan brief command to verify that VLAN 20 is no longer in the vlan.dat file.
Alternatively, the entire vlan.dat file can be deleted using the command delete flash:vlan.dat from privileged EXEC mode. After the switch is reloaded, the previously configured VLANs will no longer be present. This effectively places the switch into its “factory default” concerning VLAN configurations.
In Summary, VLANs are an integral part of modern network design, providing a versatile, efficient, and secure way to manage network traffic and resources. For individuals engaged in legal studies, understanding VLANs can be important, especially when dealing with cases or regulations involving network security and data privacy.
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