CCNP / BSCI Exam Tutorial: Route Summarization And The OSPF Null Interface

CCNP exam success, particularly on the BSCI exam, demands you understand the details of route summarization. This skill not only requires that you have a comfort level with binary conversions, but you have to know how and where to apply route summarization with each individual protocol.

You also have to know the "side effects" of route summarization. With OSPF, there will actually be an extra interface created at the point of summarization, and this catches a lot of CCNP candidates by surprise. Let's take a look at the null0 interface and how it relates to OSPF summarization.

On R1, the following networks are redistributed into OSPF, and then summarized.

interface Loopback16

ip address 16.16.16.16 255.0.0.0


interface Loopback17

ip address 17.17.17.17 255.0.0.0


interface Loopback18

ip address 18.18.18.18 255.0.0.0

interface Loopback19

ip address 19.19.19.19 255.0.0.0

R1(config)#router ospf 1

R1(config-router)#redistribute connected subnets

R1(config-router)#summary-address 16.0.0.0 252.0.0.0

The summary address appears on R2, a downstream router.

R2#show ip route ospf


O E2 16.0.0.0/6 [110/20] via 172.12.123.1, 00:00:05, Serial0


Let's go back to R1 and look at its OSPF table.

R1#show ip route ospf


O 16.0.0.0/6 is a summary, 00:01:51, Null0

Where did the null0 interface come from, and why is it there? Packets sent to the null interface are dropped, and in this case, that's a good thing.

When you configure summary routes in OSPF, a route to null0 will be installed into the OSPF routing table. This helps to prevent routing loops. Any packets destined for the routes that have been summarized will have a longer match in the routing table, as shown below...

C 17.0.0.0/8 is directly connected, Loopback17

C 16.0.0.0/8 is directly connected, Loopback16

C 19.0.0.0/8 is directly connected, Loopback19

C 18.0.0.0/8 is directly connected, Loopback18

O 16.0.0.0/6 is a summary, 00:01:51, Null0


.. and packets that do not match one of the summarized routes but do match the summary route will be dropped.

Preventing routing loops when performing route redistribution and summarization is vital. OSPF gives us a little help in that regard in this situation, and as you study more complex redistribution scenarios on your way to the CCNP and CCIE, you'll realize that we'll take all the help we can get!

CCNP / BCMSN Exam Tutorial: VLAN Trunking Protocol (VTP)

Passing the BCMSN exam and getting one step closer to the CCNP certification means learning and noticing details that you were not presented with in your CCNA studies. (Yes, I know – you had more than enough details then, right?) One protocol you’ve got to learn more details about is VTP, which seemed simple enough in your CCNA studies! Part of learning the details is mastering the fundamentals, so in this tutorial we’ll review the basics of VTP.


In show vtp status readouts, the "VTP Operating Mode" is set to "Server" by default. The more familiar term for VTP Operating Mode is simply VTP Mode, and Server is the default. It's through the usage of VTP modes that we can place limits on which switches can delete and create VLANs.

In Server mode, a VTP switch can be used to create, modify, and delete VLANs. This means that a VTP deployment has to have at least one switch in Server mode, or VLAN creation will not be possible. Again, this is the default setting for Cisco switches.

Switches running in Client mode cannot be used to create, modify, or delete VLANs. Clients do listen for VTP advertisements and act accordingly when VTP advertisements notify the Client of VLAN changes.

VTP Transparent mode actually means that the switch isn't participating in the VTP domain as Servers and Clients do. (Bear with me here.) Transparent VTP switches don't synchronize their VTP databases with other VTP speakers. They don't even advertise their own VLAN information! Therefore, any VLANs created on a Transparent VTP switch will not be advertised to other VTP speakers in the domain, making them locally significant only. (I know you remember that phrase from your CCNA studies!)

Devices running VTP Transparent mode do have a little something to do with the other switches in the VTP domain, though. When a switch running in Transparent mode receives a VTP advertisement, that switch will forward that advertisement to other switches in that VTP domain.

Configuring switches as VTP Clients is a great way to “tie down” VLAN creation capabilities to switches that are under your physical control. However, this occasionally leads to a situation where only the VTP clients will have ports that belong to a given VLAN, but the VLAN still has to be created on the VTP server. (VLANs can be created and deleted in transparent mode, but those changes aren't advertised to other switches in the VTP domain.)


In the next BCMSN tutorial, we’ll take a look at the details of VTP.

CCNA Certification Exam Tutorial: Cisco Switching Modes

To pass the CCNA exam and earn this important certification, you’ve got to know switching inside and out. While you’re learning all the basic switching theory, make sure to spend some time with the one of three switching modes Cisco routers can use.

Store-and-Forward is exactly what it sounds like. The entire frame will be stored before it is forwarded. This mode allows for the greatest amount of error checking, since a CRC (Cyclical Redundancy Check) is run against the frame before it is forwarded. If the frame contains an error, it is discarded. If there’s no problem with the frame, the frame is then forwarded to its proper destination.


While store-and-forward does perform error checking, the delay in processing the frame while this error check is run results in higher latency than the other modes you’re about to read about. The latency time can also vary, since not all frames are the same size.

Cut-through switching copies only the destination MAC address into its memory before beginning to forward the frame. Since the frame is being forwarded as soon as the destination MAC is read, there is less latency than store-and-forward. The drawback is that there is no error checking.

There is a middle ground, fragment-free switching. Only part of the frame is copied to memory before it is forwarded, but it’s the first 64 bytes of the frame, not just the destination MAC. (Why? Because if there is a problem with the frame, it’s most likely in the first 64 bytes.) There is a little more error checking than cut-through, but not as much latency as with store-and-forward.

Note that the latency of both cut-through and fragment-free is fixed; these modes always look at the first six or 64 bytes, respectively. Store-and-forward's latency depends on the size of the frame.
Learning the similarities and differences between these modes is an often-overlooked part of CCNA studies. Spend some time studying this important CCNA topic – you’ll be glad you did!

CCNA / MCSE / CCNP Certification: Making Failure Work For You

Whether you're on the road to the CCNA, CCNP, MCSE, or you're on any other computer certification track, the odds are that sooner or later, you're going to fail an exam. It's happened to almost all of us, yours truly included. What you have to keep in mind in these times is that success is not a straight line. You've probably seen charts showing the growth of an industry or a business -- you know, the ones that go from left to right, and look kind of jagged. The line goes up for a while, then down a bit, then up some more, then down a little.

The key? While every business has its setbacks, the net result is that the line goes up and progress is made. That's how you want your certification pursuit and your career to go as well - upward!

I'm not asking you to be happy about failing an exam. You're allowed to get mad for a few minutes, vow to never take another exam again, and be disappointed. What you're not allowed to do is stay that way.

If you put your books away in a fit of anger, get them out. If you took some time off, it's time to get back to work. Again, there's nothing wrong with being unhappy about failing an exam. It's how you handle that failure that counts. No inventor, executive, or entrepreneur has ever been right 100% of the time. Learn something from your failure. Was your study time quality study time? Did you get some hands-on practice with the technology you're studying? Asking yourself these questions can be tough, but it can be highly valuable in making sure you don't fail the next time. And there must be a next time - because the one thing you cannot do is quit.

Besides, take it from someone who's been there - your temporary failure makes your eventual success that much sweeter.

CCNA / CCNP Home Lab Tutorial: The VLAN.DAT File

CCNA and CCNP candidates who have their own Cisco home labs often email me about an odd situation that occurs when they erase a switch's configuration. Their startup configuration is gone, as they expect, but the VLAN and VTP information is still there!

Sounds strange, doesn't it? Let's look at an example. On SW1, we run show vlan brief and see in this abbreviated output that there are three additional vlans in use:

SW1#show vlan br


10 VLAN0010 active

20 VLAN0020 active

30 VLAN0030 active

We want to totally erase the router's startup configuration, so we use the write erase command, confirm it, and reload without saving the running config:

SW1#write erase

Erasing the nvram filesystem will remove all configuration files! Continue?

[confirm]

[OK]

Erase of nvram: complete


00:06:00: %SYS-7-NV_BLOCK_INIT: Initalized the geometry of nvram

SW1#reload

System configuration has been modified. Save? [yes/no]: n

Proceed with reload? [confirm]

The router reloads, and after exiting setup mode, we run show vlan brief again. And even though the startup configuration was erased, the vlans are still there!

Switch#show vlan br


10 VLAN0010 active

20 VLAN0020 active

30 VLAN0030 active

The reason is that this vlan and VTP information is actually kept in the VLAN.DAT file in Flash memory, and the contents of Flash are kept on a reload. The file has to be deleted manually.

There's a little trick to deleting this file. The switch will prompt you twice to ask if you really want to get rid of this file. Don't type "y" or "yes"; just accept the defaults by hitting the return key. If you type "y", the router attempts to delete a file named "y", as shown here:

Switch#delete vlan.dat

Delete filename [vlan.dat]? y

Delete flash:y? [confirm]

%Error deleting flash:y (No such file or directory)



Switch#delete vlan.dat

Delete filename [vlan.dat]?

Delete flash:vlan.dat? [confirm]


Switch#

The best way to prepare for CCNA and CCNP exam success is by working on real Cisco equipment, and by performing lab tasks over and over. Repetition is the mother of skill, and by truly erasing your VLAN and VTP information by deleting the vlan.dat file from Flash, you'll be building your Cisco skills to the point where your CCNA and CCNP exam success is a certainty.

CCNA / CCNP Home Lab Tutorial: Assembling Your Cisco Home Lab

A CCNA or CCNP candidate who wants to be totally prepared for their exams is going to put together a home lab to practice on. With used Cisco routers and switches more affordable and plentiful then ever before, there's really no excuse to not have one!

With the many different models available, there is some understandable confusion among future CCNAs and CCNPs about which routers to buy and which ones to avoid. You can take almost any set of Cisco routers and put together a home lab; part of the learning process is taking what equipment you have available and putting together your own lab! For those of you preparing to start your home lab or add to your existing one, this article will list the routers I use in my Cisco pods. You certainly don't have to have all this equipment, but this will give you some good ideas on how to get started.

The most versatile router you can get for your CCNA / CCNP home lab is a 2520. These routers come with four serial ports, one ethernet port, and one BRI interface for ISDN practice. This mix of interfaces means you can actually use it as a frame relay switch while using the ethernet and BRI ports for routing. (There is no problem with using a lab router as both your frame relay switch and a practice router; for a frame relay switch sample configuration, visit my website!)

My pods consist of five routers and two switches, and three of the five routers are 2520s, due to their versatility. A recent ebay search showed these routers selling for $99 - $125, an outstanding value for the practice you're going to get.

I also use 2501s in my home labs. These have fewer interfaces, but the combination of two serial interfaces and one ethernet interface allows you to get plenty of practice.

A combination that works very well is using three 2520s; one as my dedicated frame relay switch, one as R1, and another as R2. Add a 2501 as R3, and you can have a frame cloud connecting R1, R2, and R3, a direct serial connection between R1 and R3, an Ethernet segment that includes all three routers, and an ISDN connection between R1 and R2 if you have an ISDN simulator. That combination will allow you to get a tremendous amount of practice for the exams, and you can always sell it when you're done!

2501s are very affordable, with many in the $50 range on ebay. It's quite possible to get three 2520s and one 2501 for less than $500 total, and you can get most of that money back if you choose to sell it when you're done.

With four routers to work with, you're probably going to get tired of moving that console cable around. An access server (actually a Cisco router, not the white boxes we tend to think of when we hear "server") will help you out with that. An access server allows you to set up a connection with each of your other routers via an octal cable, which prevents you from moving that console cable around continually. For an example of an access server configuration, just visit my website and look in the "Free Training" section.

Access server prices vary quite a bit; don't panic if you do an ebay search and see them costing thousands of dollars. You do NOT need an expensive access server for your CCNA / CCNP home lab. 2511s are great routers to get for your access server.

One question I get often from CCNA / CCNP candidates is "What routers should I buy that I can still use when I'm ready to study for the CCNP?" The CCIE lab changes regularly and sometimes drastically when it comes to the equipment you'll need. During my CCIE lab studies, I found that renting time from online rack rental providers was actually the best way to go. Don't hesitate when putting your CCNA / CCNP home lab together, wondering what will be acceptable for the CCIE lab a year or so from now. None of us know what's going to be on that equipment list, so get the CCNA and CCNP first - by building your own Cisco home lab!

CCNA

CCNA stands for Cisco Certified Network Associate - a certification for IT professionals that is issued by Cisco Systems, Inc., one of the most successful computer networking companies. Cisco manufactures and markets a wide range of devices for both enterprises and telecommunications carriers. Cisco is an abbreviation of San FranCISCO.

The Cisco Certified Network Associate is an apprentice, or foundation level (along with Cisco Certified Design Associate), within the three levels of certification that include Associate, Professional, and Expert. Basically, CCNA professionals are certified to install, configure, and operate LAN, WAN, and dial access services for small networks (100 nodes or fewer), including but not exclusive to use of these protocols: IP, IGRP, Serial, Frame Relay, IP RIP, VLANs, RIP, Ethernet, and Access Lists. The certification is valid for three years, after which recertification may be sought.

In order to hold a CCNA certification, a candidate has to pass either the Cisco Certified Network Associate Exam or a combination of Introduction to Cisco Networking Technologies Exam and Interconnecting Cisco Networking Devices Exam. Main topics for these three exams include Planning and Designing; Design and Support; Implementation and Operation; Troubleshooting; and Technology. Other related topics may also appear on any specific delivery of the exam.

There are also some recommended training programs that may be taken before the above-mentioned examinations. These programs include Introduction to Cisco Networking Technologies (INTRO), Interconnecting Cisco Network Devices (ICND), and Additional Training (CCNA Prep Center Pilot). These trainings incorporate topics such as fundamental knowledge and comprehension of networking; how to select, connect, configure, and troubleshoot the various Cisco networking devices; sample questions, simulations, e-learning modules, labs, tips, etc.

Boost Your Career And Benefit From A Microsoft Certification Or Two Or Three!

You went to college and thought you were prepared for the job market. If you are going for entry-level work, yeah, you are prepared. However, to really get ahead, you need Microsoft certification, whether it is an MCP, MCSA, MCSE or any other string of letters. Quite a few people will go for multiple certifications to broaden their experience and scope of possible job opportunities.

Some of the Microsoft certifications require you have to have at least one year of practical experience in order to pursue a certification, namely an MCSE or Microsoft Certified Systems Engineer. It is important to have that experience that these certain certifications require because the training, like the MCSE training and the MCSE exams that follow, are very intense. In fact, some people will not only partake of the standard MCSE training, but also MCSE boot camps for more in-depth studies into their certification.

One standard benefit to having a Microsoft certification is that it is a great basic means of analyzing the aptitude of an employee. If you are a manager or owner in a business, you want some way to evaluate that employee’s skills. And if you are the employee, you know that your boss recognizes your abilities.

If you are on the hunt for a new job, then potential hiring managers and employers have a basis in which to assess your qualifications. Without that Microsoft certification on your resume, these employers would have no idea about your skills and most likely would consider someone else, someone with a certification, for the position you were aiming for.

If you do not have much hands-on experience in your field, but you do have the Microsoft certification to prove that you know the material, you would also have a leg up on anyone else applying for the same position that may have more hands-on experience, but no certification. For some reason, that certification, those little string of letters like MCP or MCSE, hold a lot of power.

Yet another benefit to holding a Microsoft certification or two is the money aspect of it all. Sure, you shelled out some major bucks to fund your education in those MCP courses or that MCSE training, but consider it an investment in yourself. With certification, you can bargain a higher salary and even reimbursement for your training!

Many professionals in the IT field or in a company in which you work in an IT department could benefit from Microsoft certification. Do you work as an Administrator for a network, mail or web server? Are you involved in the security of networks and the internet? Any of those positions and much more benefit with additional training and certification. Just think money! It is the biggest motivator. The more you know and can bring to a position, the more money you stand to make.

So think about going for your MCSE or MCP certification or any number of others available. More training; more knowledge; more money ... sounds like a no-brainer! Go nuts and get certified today!