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Virtual LAN and Virtual Private Network (VLAN VPN)


November 1, 2016
Published By : Pratik Kataria
Categorised in:


A VLAN allows a network administrator to create groups of logically networked devices that act as if they are on their own independent network, even if they share a common infrastructure with other VLANs.
Using VLANs, you can logically segment switched networks based on functions, departments, or project teams.
You can also use a VLAN to geographically structure your network to support the growing reliance of companies on home-based workers.
These VLANs allow the network administrator to implement access and security policies to particular groups of users.

A VLAN is a logically separate IP subnetwork.
VLANs allow multiple IP networks and subnets to exist on the same switched network.
For computers to communicate on the same VLAN, each must have an IP address and a subnet mask that is consistent for that VLAN.
The switch has to be configured with the VLAN and each port in the VLAN must be assigned to the VLAN.

A switch port with a singular VLAN configured on it is
called an access port.
Remember, just because two computers are physically connected to the same switch does not mean that they can communicate.
Devices on two separate networks and subnets must communicate via a router (Layer 3), whether or not VLANs are used.


Benefits of VLAN

Security – Groups that have sensitive data are separated from the rest of the network, decreasing the chances of confidential information breaches.
–-Faculty computers are on VLAN 10 and completely separated from student and guest data traffic.

Cost reduction – Cost savings result from less need for expensive network upgrades and more efficient use of existing bandwidth and uplinks.

Higher performance – Dividing flat Layer 2 networks into multiple logical workgroups (broadcast domains) reduces unnecessary traffic on the network and boosts performance.

Broadcast storm mitigation – Dividing a network into VLANs reduces the number of devices that may participate in a broadcast storm.
–-In the figure you can see that although there are six computers on this network, there are only three broadcast domains: Faculty, Student, and Guest.

Applications of VLAN

Simpler project or application management – VLANs aggregate users and network devices to support business or geographic requirements.

Having separate functions makes managing a project or working with a specialized application easier, for example, an e-learning development platform for faculty.
It is also easier to determine the scope of the effects of upgrading network services.

Virtual Private Network (VPN)

Virtual Private Network is a type of private network that uses public telecommunication, such as the Internet, instead of leased lines to communicate.

Became popular as more employees worked in remote locations.

Terminologies to understand how VPNs work.

Traditional Connectivity


Private Network vs Virtual Private Network

Employees can access the network (Intranet) from remote locations.

Secured networks.

The Internet is used as the backbone for VPNs

Saves cost tremendously from reduction of equipment
and maintenance costs.


Remote Access Virtual Private Network


Brief Overview of How it Works

Two connections – one is made to the Internet and the second is made to the VPN.
Datagrams – contains data, destination and source information.
Firewalls – VPNs allow authorized users to pass through the firewalls.
Protocols – protocols create the VPN tunnels.

Four Critical Functions

Authentication – validates that the data was sent from the sender.
Access control – limiting unauthorized users from accessing the network.
Confidentiality – preventing the data to be read or copied as the data is being transported.
Data Integrity – ensuring that the data has not been altered


Encryption — is a method of “scrambling” data before transmitting it onto the Internet.

Public Key Encryption Technique

Digital signature – for authentication


A virtual point-to-point connection made through a public network. It transports encapsulated datagrams.

Two types of end points:

  • Remote Access
  • Site-to-Site

VPN Encapsulation of Packets


Types of Implementations

What does “implementation” mean in VPNs?

3 types

  • Intranet – Within an organization
  • Extranet – Outside an organization
  • Remote Access – Employee to Business

Applications: Site-to-Site VPNs

Large-scale encryption between multiple fixed sites such as remote offices and central offices

Network traffic is sent over the branch office Internet connection

This saves the company hardware and management expenses

Applications:  Remote Access

Encrypted connections between mobile or remote users and their corporate networks
Remote user can make a local call to an ISP, as opposed to a long distance call to the corporate remote access server.
Ideal for a telecommuter or mobile sales people.
VPN allows mobile workers & telecommuters to take advantage of broadband connectivity. i.e. DSL, Cable

Industries That May Use a VPN

Healthcare: enables the transferring of confidential patient information within the medical facilities & health care provider

Manufacturing: allow suppliers to view inventory & allow clients to purchase online safely

Retail: able to securely transfer sales data or customer info between stores
& the headquarters

Banking/Financial: enables account information to be transferred safely within departments & branches

General Business: communication between remote employees can be securely exchanged