Network technologies and trends » Layer 2

What are Private VLANs (PVLANS)?

Yasir Irfan — Tue, 18 Jan 2011 11:39:37 +0000

If you are working hard towards achieving Cisco CCNP Switch 642-813 certification exams, private VLANs does comes into picture. Yeah its part of CCNP Switch 642-813 curriculum. Cisco basically designed Private VLANs (PVLANS) as part of layer 2 security, in normal condition in any given network the traffic is allowed to move unconditionally within a VLAN. What if you want to restrict the movement of traffic with in a VLAN? Private VLAN (PVLANS) comes into picture.

Private VLAN (PVLANS) are really just sub-VLAN inside a VLAN, they basically allows you to split the VLAN domain into multiple isolated subdomains. When it comes to inter-VLAN routing we need a Layer 3 device to forward packets. The same analogy applies to Private VLAN (PVLANS). They need layer 3 devices such as Cisco Router or Cisco Multilayer Switch.

To make things much simpler, consider a Network environment in which the service provider need to connects servers belonging to different customers to the Internet. These servers must all be able to reach their first-hop router, but for security reasons, servers belonging to one customer must not be able to communicate with servers belonging to another. An obvious design solution for these requirements is to place each customer’s servers in a separate VLAN, which also requires the assignment of a separate IP subnet per customer (even if they have only one server).

By creating separate VLANs not only wastes the VLAN IDs but also IP addresses as well. To overcome this Private VLAN (PVLANS) were introduced as a more elegant alternative, allowing multiple devices to reside in the same IP subnet, yet remain isolated from one another at layer two.

In upcoming post we see what terminologies are used in Private VLAN (PVANS) and how they are distinguished.

Cisco Press releases “Interconnecting Data Centers Using VPLS”

Yasir Irfan — Wed, 08 Jul 2009 10:02:27 +0000

Cisco Press just released the book “Interconnecting Data Centers Using VPLS (Ensure Business Continuance on Virtualized Networks by Implementing Layer 2 Connectivity Across Layer 3)” . This book deals with the interconnection of Data Centers using VPLS . Virtualization techniques were developed to solve many problems with business continuance; however these solutions now pose severe network challenges and business continuance issues of their own. This book describes Cisco’s break-through solutions that evolve your network toward support of server virtualization techniques ensuring a highly-resilient network solution by implementing Layer 2 connectivity across Layer 3 network infrastructure using VPLS.

· Interconnecting Data Centers Using VPLS (Ensure Business Continuance on Virtualized Networks by Implementing Layer 2 Connectivity Across Layer 3)
By Nash Darukhanawalla, Patrice Bellagamba.

· Published by Cisco Press.

· Series: Networking Technology.

http://www.ciscopress.com/bookstore/product.asp?isbn=1587059924Source:

www.ciscopress.com

VLAN Trunking Protocol (VTP) Overview – Series 5

Yasir Irfan — Fri, 17 Apr 2009 04:42:51 +0000

These days I am in Bangalore with my parents just enjoying my holidays. Guess what today night I am travelling to Singapore and Malaysia with my wife. May be I will not be in a position post more posts this month as I am relaxing and enjoying the beauty of Nature. For sure I am going to share the natural beauty with all you guys.

Mean while before departing to Singapore I thought let me continue my series on VTP , in this series let s focus on VTP modes. There three type of VTP modes

a) VTP Server

b) VTP Client

c) VTP Transparent

VLAN Trunking Protocol (VTP) Overview – Series 4

Yasir Irfan — Mon, 09 Mar 2009 05:14:36 +0000

What do you think what happens? If a new Cisco Catalyst® switch is placed between any two VTP domains, the Cisco Catalyst® switch will join the VTP domain identified by the first VTP update it receives. Just check the below example.

The VTP domain can be changed to another in a Cisco Catalyst® switch by using the CLI prompt, this is the only way you can change.

VLAN Trunking Protocol (VTP) Overview – Series 3

Yasir Irfan — Wed, 25 Feb 2009 11:23:45 +0000

In Cisco Catalyst® switches the VTP domain can be added through CLI configuration or else it can be learnt from an adjacent VTP Cisco Catalyst® switch. Let’s see this from the below example

Switch C is added to the network connecting via a trunk port to Switch B with no VTP domain configured, in this mode when the Switch C receives the first VTP update from the adjacent Switch B , it will become the part of the VTP domain ITKE as identified in the VTP update.

VLAN Trunking Protocol (VTP) Overview – Series 2

Yasir Irfan — Mon, 23 Feb 2009 06:35:13 +0000

In my previous post I just introduced the VLAN trunking protocol; let’s talk about the VTP domain.

The VTP domain consists of a group of logical group of Cisco Catalyst Switches that are part of the same VTP management domain. A Cisco Catalyst Switch can belong only to one VTP domain at any time,

The VTP domain is a logical group of switches that will share VLAN information. Each switch can belong only to one VTP domain in addition to sharing the VLAN information with all other Cisco Catalyst Switches in the same VTP domain. Cisco Catalyst Switches in different VTP domains drops any VTP updates received from Cisco Catalyst Switches.

VLAN Trunking Protocol (VTP) Overview – Series 1

Yasir Irfan — Sat, 21 Feb 2009 06:21:03 +0000

What is a VLAN Trunking Protocol (VTP)?

VLAN Trunking Protocol (VTP) is a Cisco proprietary Layer 2 messaging protocol that manages the addition, deletion, and renaming of VLANs for the Cisco Catalyst Switches in the same VLAN Trunking Protocol (VTP) domain. VLAN Trunking Protocol (VTP) enables Cisco Catalyst Switches to exchange and maintain consistent VLAN information amongst a group of Cisco Catalyst Switches.

For example, information for the VLAN 50 defined in Cisco Catalyst Switch A is propagated via VTP updates to all other Cisco Catalyst Switches (Switches B, C and D) in the same VTP domain, the other Cisco Catalyst Switches B, C and D will all end up adding VLAN 50 in their local VLAN data base. VTP is available on most of the Cisco Catalyst Family products.

The comparable IEEE standard in use by other manufacturers is GVRP.