This document discusses virtual local area networks (VLANs). It defines VLANs as logically segmenting switched networks based on functions, project teams, or applications, regardless of physical location or network connections. VLANs divide stations into logical groups through software instead of physical segments, allowing easy movement of stations between groups without changing physical configurations. Common VLAN types include port-based, MAC address-based, and protocol-based. Benefits of VLANs include logical organization of networks, easy moves and additions of workstations, flexible configuration changes, traffic control, and improved security.
2. What is LAN??
– A Local Area Network (LAN) was originally defined as a network of computers
located within the same area
– Local Area Networks are defined as a single broadcast domain. This means that
if a user broadcasts information on his/her LAN, the broadcast will be received
by every other user on the LAN.
– Broadcasts are prevented from leaving a LAN by using a router. The
disadvantage of this method is routers usually take more time to process
incoming data compared to a bridge or a switch.
3. What is Virtual LAN??
– Virtual Local area network is termed as VLAN.
– VLANs provide segmentation based on broadcast domains.
– VLANs logically segment switched networks based on the functions, project
teams, or applications of the organization regardless of the physical location or
connections to the network.
– All workstations and servers used by a particular workgroup share the same
VLAN, regardless of the physical connection or location.
4. More About VLAN
– The total stations(computers) are divided into logical groups instead ofphysical
segments.
– It is possible to move one station from one group to any other group without
changing the physical connections(configuration) because membership of group
is defined by software and not by hardware.
– VLAN is extremely handy where the connections are spread over multiple
buildings or departments.
6. Types of VLAN
– Port Based: Most common configuration method. Port assign individually, in
group, in rows, or across 2 or more switches. Simple to use.
– MAC Address: Rarely implemented today. Each address must be entered into
the switch and configured individually. User find it useful.
– Protocol Base: Configured like MAC address, but instead uses a logical or IP
address. No longer common because of DHCP.
7. VLAN Membership
Static Membership
– Static VLANs are also referred to as
port-based VLANs. Static VLAN
assignments are created by
assigning ports to a VLAN.
– As a device enters the network, the
device automatically assumes the
VLAN of the port.
– If the user changes ports and needs
access to the same VLAN, the
network administrator must
manually make a port-to-VLAN
assignment for the new
connection.
Dynamic Membership
– Dynamic VLANs are created using
software or by protocol.
– With a VLAN Management Policy
Server (VMPS), an administrator can
assign switch ports to VLANs
dynamically based on information of
the source MAC address of the
device connected to the port or the
username used to log onto that
device.
– As a device enters the network, the
switch queries a database for the
VLAN membership of the port that
device is connected to.
8. Protocols and Designs.
– IEEE 802.1Q
– The protocol most commonly used
today to support VLANs is IEEE
802.1Q.
– It is open standard i.e. it is available for
all to use.
– It works with ethernet only.
– Only 4 byte tag will be added to the
original frame
– Cisco Inter-Switch Link
– It is CISCO proprietary.
– This protocol used to interconnect
switches and maintain VLAN
information as traffic travels
between switches on trunk links.
– It adds 30 bytes of tags.
– ISL is available only on some Cisco
equipment.
9. Benefits of VLAN
– The key benefit of VLANs is that they permit the network administrator to
organize the LAN logically instead of physically.
– This means that an administrator is able to do all of the following:
1. Easily move workstations on the LAN.
2. Easily add workstations to the LAN.
3. Easily change the LAN configuration.
4. Easily control network traffic. Improve security