Maintain your old Siemens Hipath system

Vlans

In order to implement VLANs in a network environment, you'll need a Layer 2 switch that supports them. Almost all switches sold today that are described as "managed" switches provide the ability to make ports members of different VLANs. However, switches that don't provide any configuration function (such as many basic, lower-end switches) don't provide the ability to configure VLANs. Almost any Cisco Catalyst switch that you'll come across today provides the ability to make ports part of different VLANs.

Before getting into the details of how a VLAN functions, it's worth exploring some of the advantages that a VLAN provides. First and foremost, VLANs provide the ability to define broadcast domains without the constraint of physical location. For example, instead of making all of the users on the third floor part of the same broadcast domain, you might use VLANs to make all of the users in the HR department part of the same broadcast domain. The benefits of doing this are many. Firstly, these users might be spread throughout different floors on a building, so a VLAN would allow you to make all of these users part of the same broadcast domain. To that end, this can also be viewed as a security feature - since all HR users are part of the same broadcast domain, you could later use policies such as access lists to control which areas of the network these users have access to, or which users have access to the HR broadcast domain. Furthermore, if the HR department's server were placed on the same VLAN, HR users would be able to access their server without the need for traffic to cross routers and potentially impact other parts of the network.

VLANs are defined on a switch on a port-by-port basis. That is, you might choose to make ports 1-6 part of VLAN 1, and ports 7-12 part of VLAN 2. There's no need for ports in the same VLAN to be contiguous at all - you could make ports 1, 3 and 5 on a switch part of VLAN 1, for example. On almost all switches today, all ports are part of VLAN 1 by default. If you want to implement additional VLANs, these must first be defined in the switch's software (such as the IOS on a Cisco switch), and then ports must be made members of that VLAN. A VLAN isn't limited to a single switch, either. If trunk links are used to interconnect switches, a VLAN might have 3 ports on one switch, and 7 ports on another, as shown below. The logical nature of a VLAN makes it a very effective tool, especially in larger networking environments.

Inter-VLAN Communication

I mentioned a few times already that a VLAN is simply a special type of broadcast domain, in that it is defined on a switch port basis rather than on traditional physical boundaries. Recall from the earlier articles in this series that when a host in one broadcast domain wishes to communicate with another, a router must be involved. This same holds true for VLANs. For example, imagine that port 1 on a switch is part of VLAN 1, and port 2 part of VLAN 99. If all of the switch's ports were part of VLAN 1, the hosts connected to these ports could communicate without issue. However, once the ports are made part of different VLANs, this is no longer true. In order for a host connected to port 1 to communicate with another connected to port 2, a router must be involved.

You may already be familiar with the concept of a Layer 3 switch. A Layer 3 switch is generally a Layer 2 switching device that also includes the ability to act as a router, usually through the use of additional hardware and software features. If a switch includes Layer 3 capabilities, it can be configured to route traffic between VLANs defined in the switch, without the need for packets to ever leave the switch. However, if a switch only includes Layer 2 functionaility, an external router must be configured to route traffic between the VLANs. In some cases, it's entirely possible that a packet will leave switch port 1, be forwarded to an external router, and then be routed right back to port 2 on the originating switch. For this reason, many companies have decided to implement Layer 3 switches strategically throughout their network. Regardless of the method chosen, it's most important for you to recognize that when a host on one VLAN wants to communicate with a host on another, a router must somehow be involved.

Extending VLANs Between Switches

In order to extend VLANs across different switches, a trunk link must interconnect the switches. Think of a trunk link as being similar to an uplink between hubs - usually a trunk link is implemented between fast switch ports on two different switches using a crossover cable. For example, you might interconnect two Gigabit Ethernet ports on different switches using fiber optics, or two 100 Mbps switch ports using a traditional Cat5 crossover cable. In most cases it is generally recommended that you use the fastest port available for trunk connections, since this link will often carry a great deal of traffic, possibly for multiple VLANs.

To begin, let's assume that you have connected a link between the 100 Mbps ports of two switches, as shown below. Notice that each of these ports are members of VLAN 1 on each switch. By default, without any additional configuration, these ports will act as a trunk link, but will only pass traffic for the VLAN associated with their port connections - VLAN 1. This type of link, where only traffic for a single VLAN is passed, is referred to as an "Access Link". While an access link does the job for a single VLAN environment, multiple access links would be required if you wanted traffic from multiple VLANs to be passed between switches. Having multiple access links between the same pair of switches would be a big waste of switch ports. Obviously another solution is required when traffic for multiple VLANs needs to be transferred across a single trunk link. The solution for this comes through the use of VLAN tagging.

VLAN Tagging

When you want traffic from multiple VLANs to be able to traverse a link that interconnects two switches, you need to configure a VLAN tagging method on the ports that supply the link. Although there are a number of tagging methods in use for different technologies, the two that you need to be aware of for the purpose of the CCNA exam are known as InterSwitch Link (ISL) and 802.1q. ISL is a Cisco proprietary VLAN tagging methods, while 802.1q is a open standard. When interconnecting two Cisco switches, ISL is usually the best choice, but if you need to interconnect switches of different types (a Cisco switch and an Avaya switch, for example), then you'll need to use IETF.

For the CCNA exam, the only thing that you really need to know about 802.1q is that it is the open standard for VLAN tagging, and should be used in mixed environments. The exam expects you to have a somewhat deeper understanding of ISL, including how it works, when it can be used, and ultimately, its purpose.

First and foremost, you need to be aware that ISL will only function on ports with a speed of 100 Mbps or greater. That is, you cannot use ISL in conjunction with a 10 Mbps port. That shouldn't be an issue, since most Cisco Catalyst switches provide at least one or two Fast Ethernet ports, even on lower-end models like the 1912. Secondly, the ports on either end of the link need to support and be configured for ISL.

ISL is referred to as a VLAN tagging method. Essentially, what ISL does is tag a frame as it leaves a switch with information about the VLAN that the frame belongs to. For example, if a frame from VLAN 99 is leaving a switch, the ISL port will add information to the frame header, designating that the frame is part of VLAN 99. When this ISL frame reaches the port at the other end of the switch, it will look at the ISL header, determine that the frame is meant for VLAN 99, will strip off the ISL information, and will forward it into VLAN 99. One of the issues with VLAN tagging is that by adding information to an Ethernet frame, the size of the frame can move beyond the Ethernet maximum of 1518 bytes, to 1522 bytes. Because of this, all non-ISL ports will see frames larger than 1518 bytes as giants, and as such, invalid. This is the reason why a port needs to be configured for ISL in order for it to understand this different frame format.

One VLAN tagging is configured on the ports associated with the link connecting switches, the link is known as a "Trunk Link". A trunk link is capable of transferring frames from many different VLANs through the use of technologies like ISL or 802.1q.

A better strategy here would be to configure ISL tagging on one of the router's Fast Ethernet interfaces, and then configure ISL on the connected switch port. This configuration, also known as a "router on a stick", would allow the router to process the traffic of multiple VLANs, and route traffic between them. We'll get into the details of routing within the next few articles.

Beyond its intended purpose of configuring trunk links between switches, ISL is often used in other ways. For example, it is possible to purchase network interface cards that support ISL. If a server were configured with an ISL-capable network card, it could be connected to an ISL port on a switch.

This would allow a server to be made part of multiple VLANs simultaneously, the benefit being that hosts from different broadcast domains could then access the server without the need for their packets to be routed. While this may seem like a perfect solution, you need to remember than the server would now see all traffic from these VLANs, which could negatively impact performance.

I hope this article has provided you the good information about the Vlans.

This articles is submitted by Kashif Raza http://www.networkingtutorials.net

In The News:

'US no migrant camp' - Trump on tough border policy
Mon, 18 Jun 2018 17:30:00 +0100
US President Donald Trump has defended the policy of separating migrant children from their parents at border camps.

One dead and four wounded in Sweden shooting
Mon, 18 Jun 2018 19:59:00 +0100
One person has died and four injured in a shooting in the Swedish city of Malmo.

Rapper XXXTentacion shot dead in Florida
Mon, 18 Jun 2018 23:15:00 +0100
Rapper XXXTentacion has been shot dead in south Florida.

Kim Jong Un visits China after denuclearisation summit
Tue, 19 Jun 2018 05:22:00 +0100
North Korean leader Kim Jong Un is beginning a two-day visit to China, following his summit with Donald Trump in Singapore last week.

Being married is good for the heart
Tue, 19 Jun 2018 04:31:00 +0100
Married people are less likely to develop heart disease or have a stroke than those who are single, according to new research.



tikatoshop.it

Erfahrungen mit Pallhuber Wein
Agen Bola SBOBET Terpercaya

Travel in comfort and at your leisure with CT Airlink Limousine & Car Service for top quality private transportation and exceptional customer service. We operate Sedans, SUVs & Vans for CT Car Services to covering all Connecticut airports including Car Service from CT to Newark Airport , Mohegan Casino Uncasville CT, Foxwoods Casino Mashantucket CT, Manhattan Cruise Terminal NYC, Brooklyn Cruise Terminal NYC and Bayonne Cruise Terminal NJ. CT Airlink hire licensed and friendly chauffeurs who have in-depth knowledge of the Areas.

Professional XP Style Icons in Software and Website Development

Using professional icons in your application or website can bring... Read More

MCP Market News: Microsoft SQL Server & SQL Reporting Services

Are you ready? SQL Server 2005, the next-generation data management... Read More

RFID: Strengthen the Position for SAP; United States

SAP Inc., a global leader in client/server enterprise application software... Read More

Partitioning, Formatting and Reinstalling in Windows 98

Formatting and reinstalling windows 98 is very easy if you... Read More

7 Things to Consider Before Buying Small Business Accounting Software

The world of small business accounting software can be a... Read More

Understanding Document Management

The term "document management" and "paperless office" is the subject... Read More

Microsoft Great Plains Implementation ? Overview for IT Director/Controller

What is installation in the language of technology? Installation... Read More

How a Bug Challenges to a Software Professional

It is really interesting that a bug can create problem... Read More

S is for Spying, Surveillance -- and for Software as Well

Words we choose to describe things and phenomena often show... Read More

Great Plains Customization Upgrade? Overview For CIO/IT Director

Around the same time Microsoft made its move with .Net... Read More

Free Software - Powerful Alternatives to Budget-Busting Software

When you buy a computer, it most likely comes with... Read More

5 Time-Saving Tips in Microsoft Word

Whether you have used Microsoft Word for years, have just... Read More

How to Upgrade Dexterity Customization ? Tips for IT Manager

If you have Microsoft Great Plains and support it... Read More

Software Development in 2005 - Back to the Future

2005 ? Back to the Future.What does the future hold?... Read More

Microsoft Great Plains: Customization Upgrade & Recovery ? Visual Studio VB 6.0

Microsoft Great Plains, former Great Plains Software Dynamics, eEnterprise has... Read More

SpyBot - Search and Destroy versus Microsoft AntiSpyware (Beta).... My personal experiences...

Ok... Where to start?Well, I guess I will start at... Read More

Great Plains Dexterity: Customizations & Source Code Programming

Great Plains Software Dynamics, Dynamics C/S+, eEnterprise were written on... Read More

Secure File Transfer Using SSH Plus Additional Audit & Automation - FSA Reporting

In order to meet regulatory and corporate compliance requirements reporting... Read More

Getting Technical Support Help Online

Sometimes your PC will start acting strange for no apparent... Read More

Most Dangerous Types of Spyware are on the Rise: How to Choose the Weapon

Bad News - the Threat is Bigger than it SeemedHow... Read More

A Simple Guide To Wikis

A wiki is an editable text-based website. But you don't... Read More

Bill of Lading ? Custom Reporting for Microsoft Great Plains ? Overview for Consultant

Bill of Lading is required report for Logistics and Freight... Read More

Explore the Internet in a Whole New Way

For a long time now Microsoft's Internet Explorer has ruled... Read More

Basic Tips and tricks for Windows XP

Running Applications in Compatibility Mode With Windows XP, you can... Read More

Artificial Intelligence And Intuition

The intuitive algorithm.Roger Penrose considered it impossible. Thinking could never... Read More