5 Reasons To Purchase Desktop Computers

If you are in the market for a computer, there are a number of factors to consider. Will it be used for your home, your office or perhaps even your home office combo? First off, you will need to set a budget for your new purchase before deciding whether to shop for notebook or desktop computers. Many offices use desktop computers because they are not intended to be moved around a lot. In addition, affordability often plays a large role in someone’s decision as to whether to purchase notebook or desktop computers.

While you are shopping around, it’s important to keep in mind some of the benefits that go along with owning different types of computers. To that end, this article provides five important reasons to purchase desktop computers.

- Desktop computers are typically much more affordable than notebook computers. With notebooks, you are paying more for the convenience of portability. For as little as $299.00, desktop computers can be purchased from one of the leading manufacturers and a notebook computer for as little as $499.00.
- Unlike notebook computers, replacing a keyboard, mouse, speakers or even a monitor does not require having your computer serviced by a professional repair shop. Because notebook computers have everything built in, including the aforementioned features, it is more difficult to replace a keyboard or monitor as opposed to desktop computers, which operate on external connections.

- In the event of an unlawful entry into your home, desktop computers are not as likely to be stolen because of their weight and bulk. Notebook computers, on the other hand, are small and portable. This, alone, makes them more appealing to a thief than desktop computers.

- Desktop computers are stationary by nature. Unlike a notebook computer, which can easily be moved from room to room, they are less likely to be dropped or broken because they are not moved as often.

- The vents on desktop computers are located on the back of the tower, which allows for proper ventilation that will help to prevent the computer from overheating. Notebook computers, on the other hand, feature only one vent on the back with the remaining underneath the base. If placed on a table, the air vents can become blocked and the computer may overheat. If prolonged use leads to overheating, damage may result.

When choosing from the many desktop computers on the market, always make sure that you purchase from a manufacturer who has experience in creating computers. Even though they are more affordable than notebooks, desktop computers are not cheap. With an investment that involves several hundred dollars, you will want to consider the length of time the manufacturer has been in business, their reputation with customers and their warranty.

Additionally, when choosing any system, including desktop computers, always look at the potential for future upgrading. As you grow, you will want your computer to grow with you and a part of that will include a slight upgrade from time to time. This is the only way to get the best use of your desktop computers and make sure that your investment is one that lasts for years to come.

5 Reasons For Owning A USB Flash Drive

There have been a number of wonderful inventions during the 20th and 21st century. Some of these creations have been both massive and minute. Very few of mankinds modern creations have revolutionized working life so much as the USB flash drive though. Ok now that might seem a bit much for some people but the reality remains the same - USB flash drives have made the working lives of millions of office workers, teachers, students, IT and other professionals massively more simple. If you already one (or a few) USB flash drives then you'll know just how incredibly useful they are. If you don't already own at least one USB memory stick then hopefully this article will help convince you of their absolute usefulness in both your working and personal life.

So what's so great about USB flash drives?

Small

Prior to the creation of USB flash drives all external storage devices for computers were either bulky or awkward (dozens of blank discs for example) or sometimes an annoying combination of being both bulky and awkward. USB flash drives are also called Thumb Drives because they're about the size of your thumb (although some are much smaller now) and you can easily fit several gigabytes of data in your jeans or shirt pocket thus eliminating the bulky and awkward factor straight away.

Portable

USB flash drives are about the single most portable data backup device possible. They don't require an external power source of any kind, nor do you need any cables or tools to set them up and last but not least they don't require any additional software to be installed for them to work on any modern computer (Windows XP, 2000 and Vista and most Macs) so you can quite literally pick them up and use them anywhere you want.

Reliable

Once the data is stored on a USB flash drive you can rest assured that it's going to stay there and be there when you next need it. This is totally unlike the world of floppy disks or rewriteable CD/DVD discs where they can just stop working for no apparent reason. Flash drives were built to provide consistent and reliable performance. Most of these drives come with built-in write protection to prevent you from overwriting your own important data - if you were silly enough to do so.

Tough

For years people fiddled with boxes of floppy disks and CDs/DVDs. These were bulky, easily lost and easily damaged. External hard drives also provided another method of transporting data between systems but the smallest jolt was and is enough to kill an external hard disk stone dead. USB flash drives are based on what's called Solid State Memory - this simply means that it's the same as standard computer memory in that it has no moving parts and is therefore almost impossible to damage (except for jumping up and down on it or maybe hitting it with a hammer for example. Please don't test either of these theories at home!)

Mass Storage

The first USB thumb drives only offered between 16MB and 64MB of storage space. The incredible popularity of these drives has driven the desire for more and more storage space to new heights every few months. Currently 8GB USB drives are becoming pretty common and it won't be long before the 12GB and 24GB models hit the market. To put this in perspective 8GB is enough to hold 2 full DVD quality movies or about 2,700 high quality MP3 files - surely this is enough for you? No?

The portability of the USB flash drive combined with reliability and the more than generous storage provided by such a tiny device make them the smart choice for anyone who needs to move files between PCs or simply just keep a second copy of their most precious data on a secure and reliable storage device.

Cisco CCNP Certification / BCMSN Exam Tutorial: The HSRP MAC Address

To pass the BCMSN exam and earn your CCNP, you've got to know HSRP inside and out! Part of that is knowing how the MAC address of the virtual router is derived, and another part is knowing how to change this address. We'll look at both features in this tutorial.

We've got two routers on a segment running HSRP, so first we need to find out what the MAC address of the HSRP virtual router is. The show command for HSRP is show standby, and it's the first command you should run while configuring and troubleshooting HSRP. Let's run it on both routers and compare results.

R2#show standby

Ethernet0 - Group 5

Local state is Standby, priority 100

Hellotime 3 sec, holdtime 10 sec

Next hello sent in 0.776

Virtual IP address is 172.12.23.10 configured

Active router is 172.12.23.3, priority 100 expires in 9.568

Standby router is local

1 state changes, last state change 00:00:22

R3#show standby

Ethernet0 - Group 5

Local state is Active, priority 100

Hellotime 3 sec, holdtime 10 sec

Next hello sent in 2.592

Virtual IP address is 172.12.23.10 configured

Active router is local

Standby router is 172.12.23.2 expires in 8.020

Virtual mac address is 0000.0c07.ac05

2 state changes, last state change 00:02:08

R3 is in Active state, while R2 is in Standby. The hosts are using the 172.12.123.10 address as their gateway, but R3 is actually handling the workload. R2 will take over if R3 becomes unavailable.

An IP address was statically assigned to the virtual router, but not a MAC address. However, there is a MAC address under the show standby output on R3, the active router. How did the HSRP process arrive at a MAC of 00-00-0c-07-ac-05?

Well, most of the work is already done before the configuration is even begun. The MAC address 00-00-0c-07-ac-xx is reserved for HSRP, and xx is the group number in hexadecimal. That's a good skill to have for the exam, so make sure you're comfortable with hex conversions. The group number is 5, which is expressed as 05 with a two-bit hex character. If the group number had been 17, we'd see 11 at the end of the MAC address - one unit of 16, one unit of 1.

On rare occasions, you may have to change the MAC address assigned to the virtual router. This is done with the standby mac-address command. Just make sure you're not duplicating a MAC address that's already on your network!

R2(config-if)#standby 5 mac-address 0000.1111.2222


1d12h: %STANDBY-6-STATECHANGE: Ethernet0 Group 5 state Active -> Learn


R2#show standby

Ethernet0 - Group 5

Local state is Active, priority 150, may preempt

Hellotime 4 sec, holdtime 12 sec

Next hello sent in 3.476

Virtual IP address is 172.12.23.10 configured

Active router is local

Standby router is 172.12.23.3 expires in 10.204

Virtual mac address is 0000.1111.2222 configured

4 state changes, last state change 00:00:00


1d12h: %STANDBY-6-STATECHANGE: Ethernet0 Group 5 state Listen -> Active

The MAC address will take a few seconds to change, and the HSRP routers will go into Learn state for that time period.

A real-world HSRP troubleshooting note: If you see constant state changes with your HSRP configuration, do what you should always do when troubleshooting - check the physical layer first. Best of luck on your BCMSN exam!

Cisco CCNP / BCMSN Exam Tutorial: Dynamic VLANs and VMPS

Knowledge of Dynamic VLANs and VMPS is important in your efforts to pass the BCMSN exam and earn your CCNP, and it's also a great skill to have for your networking career.

As a CCNA and CCNP candidate, you know how and why to configure static VLANs. Static VLANs can be a powerful tool for reducing unnecessary broadcast and multicast traffic, but if hosts are moved from one switch port to another, you've got to make those changes manually on the switch. With Dynamic VLANs, the changes are made - how else? - dynamically.

The actual configuration of dynamic VLANs is out of the scope of the BCMSN exam, but as a CCNP candidate you need to know the basics of VMPS - a VLAN Membership Policy Server.

Using VMPS results in port VLAN membership changes being performed dynamically, because the port's VLAN membership is decided by the source MAC address of the device connected to that port. (Yet another reason that the first value a switch looks at on an incoming frame is the source MAC address.)

In my home lab network, I've got a host connected to switch port fast0/1 that resides in VLAN 12. What if we had to move Host 1's connection to the switch to port 0/6? With static VLANs, we'd have to connect to the switch, configure the port as an access port, and then place the port into VLAN 12. With VMPS, the only thing we'd have to do is reconnect the cable to port 0/6, and the VMPS would dynamically place that port into VLAN 12.

I urge you to do additional reading regarding VMPS. Use your favorite search engine for the term configuring vmps and you'll quickly find some great official Cisco documentation on this topic.

To review, the VLAN membership of a host is decided by one of two factors. With static VLANs, the host's VLAN membership is the VLAN to which its switch port has been assigned. With dynamic VLANs, it is dependent upon the host's MAC address.

Cisco CCNA Certification Exam Tutorial: Port-Based Authentication

To pass your CCNA exam and earn this coveted certification, you must understand the details of port-based authentication. This knowledge has a great deal of value in production networks as well, since this authentication scheme is regularly implemented. Let's take a look at this particular CCNA skill.

Consider a situation where you have a server that will be connected to your switch, and you want the port to shut down if a device with a different MAC address that that of the switch attempts to connect to that port. You could also have a situation where you have someone who has a connection to a switch port in his office, and he wants to make sure that only his laptop can use that port.

Both of these examples are real-world situations, and there are two solutions for each. First, we could create a static MAC entry for that particular switch port. I don't recommend this, mainly because both you and I have better things to do than manage static MAC entries. The better solution is to configure port-based authentication on the switch.

The Cisco switch uses MAC addresses to enforce port security. With port security, only devices with certain MAC addresses can connect to the port successfully. This is another reason source MACs are looked at before the destination MAC is examined. If the source MAC is non-secure and port-based authentication is in effect, the destination does not matter, as the frame will not be forwarded. In essence, the source MAC address serves as the password.

MAC addresses that are allowed to successfully communicate with the switch port are secure MAC addresses. The default number of secure MAC addresses is 1, but a maximum of 132 secure MACs can be configured.

When a non-secure MAC address attempts to communicate with the switch port, one of three actions will occur, depending on the port security mode. In Protect mode, frames with non-secure MAC addresses are dropped. There is no notification that a violation has occurred. The port will continue to switch frames for the secure MAC address.

In Restrict mode, the same action is taken, but a syslog message is logged via SNMP, which is a messaging protocol used by Cisco routers.

In Shutdown mode, the interface goes into error-disabled state, the port LED will go out, and a syslog message is logged. The port has to be manually reopened. Shutdown mode is the default port-security mode.

Port-based authentication is just one of the many switching skills you'll have to demonstrate to earn your CCNA certification. Make sure you know the basics shown here, including the action of each particular mode, and you're on your way to CCNA exam success!

CCNP Certification / BCMSN Exam Tutorial: HSRP MAC Addresses And Timers

To earn your CCNP certification and pass the BCMSN exam, you've got to know what HSRP does and the many configurable options. While the operation of HSRP is quite simple (and covered in a previous tutorial), you also need to know how HSRP arrives at the MAC address for the virtual router - as well as how to configure a new MAC for this virtual router. This puts us in the unusual position of creating a physical address for a router that doesn't exist!

The output of show standby for a two-router HSRP configuration is shown below.

R2#show standby

Ethernet0 - Group 5

Local state is Standby, priority 100

Hellotime 3 sec, holdtime 10 sec

Next hello sent in 0.776

Virtual IP address is 172.12.23.10 configured

Active router is 172.12.23.3, priority 100 expires in 9.568

Standby router is local

1 state changes, last state change 00:00:22

R3#show standby

Ethernet0 - Group 5

Local state is Active, priority 100

Hellotime 3 sec, holdtime 10 sec

Next hello sent in 2.592

Virtual IP address is 172.12.23.10 configured

Active router is local

Standby router is 172.12.23.2 expires in 8.020

Virtual mac address is 0000.0c07.ac05

2 state changes, last state change 00:02:08

R3 is in Active state, while R2 is in Standby. The hosts are using the 172.12.123.10 address as their gateway, but R3 is actually handling the workload. R2 will take over if R3 becomes unavailable.

An IP address was assigned to the virtual router during the HSRP configuration process, but not a MAC address. However, there is a MAC address under the show standby output on R3, the active router. How did the HSRP process arrive at a MAC of 00-00-0c-07-ac-05?

Well, most of the work is already done before the configuration is even begun. The MAC address 00-00-0c-07-ac-xx is reserved for HSRP, and xx is the group number in hexadecimal. That's a good skill to have for the exam, so make sure you're comfortable with hex conversions. The group number is 5, which is expressed as 05 with a two-bit hex character. If the group number had been 17, we'd see 11 at the end of the MAC address - one unit of 16, one unit of 1.

The output of the show standby command also tells us that the HSRP speakers are sending Hellos every 3 seconds, with a 10-second holdtime. These values can be changed with the standby command, but HSRP speakers in the same group should have the same timers. You can even tie down the hello time to the millisecond, but it's doubtful you'll ever need to do that.

R3(config-if)#standby 5 timers ?

<1-254> Hello interval in seconds

msec Specify hello interval in milliseconds

R3(config-if)#standby 5 timers 4 ?

<5-255> Hold time in seconds

R3(config-if)#standby 5 timers 4 12

Another important HSRP skill is knowing how to change the Active router assignment. I'll show you how to do that, and how to configure HSRP interface tracking, in the next part of my CCNP / BCMSN exam tutorial!

CCNP Certification / BCMSN Exam Tutorial: Getting Started With HSRP

Defined in RFC 2281, HSRP is a Cisco-proprietary protocol in which routers are put into an HSRP router group. Along with dynamic routing protocols and STP, HSRP is considered a high-availability network service, since all three have an almost immediate cutover to a secondary path when the primary path is unavailable.

One of the routers will be selected as the primary ("Active", in HSRP terminology), and that primary will handle the routing while the other routers are in standby, ready to handle the load if the primary router becomes unavailable. In this fashion, HSRP ensures a high network uptime, since it routes IP traffic without relying on a single router.

The hosts using HSRP as a gateway don't know the actual IP or MAC addresses of the routers in the group. They're communicating with a pseudorouter, a "virtual router" created by the HSRP configuration. This virtual router will have a virtual MAC and IP adddress as well.

The standby routers aren't just going to be sitting there, though! By configuring multiple HSRP groups on a single interface, HSRP load balancing can be achieved.

Before we get to the more advanced HSRP configuration, we better get a basic one started! We'll be using a two-router topology here, and keep in mind that one or both of these routers could be multilayer switches as well. For ease of reading, I'm going to refer to them only as routers.

R2 and R3 will both be configured to be in standby group 5. The virtual router will have an IP address of 172.12.23.10 /24. All hosts in VLAN 100 should use this address as their default gateway.

R2(config)#interface ethernet0

R2(config-if)#standby 5 ip 172.12.23.10

R3(config)#interface ethernet0

R3(config-if)#standby 5 ip 172.12.23.10

The show command for HSRP is show standby, and it's the first command you should run while configuring and troubleshooting HSRP. Let's run it on both routers and compare results.

R2#show standby

Ethernet0 - Group 5

Local state is Standby, priority 100

Hellotime 3 sec, holdtime 10 sec

Next hello sent in 0.776

Virtual IP address is 172.12.23.10 configured

Active router is 172.12.23.3, priority 100 expires in 9.568

Standby router is local

1 state changes, last state change 00:00:22

R3#show standby

Ethernet0 - Group 5

Local state is Active, priority 100

Hellotime 3 sec, holdtime 10 sec

Next hello sent in 2.592

Virtual IP address is 172.12.23.10 configured

Active router is local

Standby router is 172.12.23.2 expires in 8.020

Virtual mac address is 0000.0c07.ac05

2 state changes, last state change 00:02:08

We can see that R3 has been selected as the Active router ("local state is Active"), the virtual router's IP is 172.12.23.10, and R2 is the standby router.

There are some HSRP values that you'll need to change from time to time. What if we want R2 to be the Active router instead? Can we change the MAC address of the virtual router? I'll answer those questions in the next part of this HSRP tutorial!