CCNP Certification / BCMSN Exam Tutorial: Server Load Balancing (SLB)

CCNP Certification / BCMSN Exam Tutorial:  Server Load Balancing (SLB)

You need to know all about router redundancy strategies to become a CCNP, but there's an important server redundancy feature you need to know as well!  Learn all about Server Load Balancing from Chris Bryant, CCIE #12933.


When you're working on your BCMSN exam on your way to CCNP certification, you'll read at length about how Cisco routers and multilayer switches can work to provide router redundancy - but there's another helpful service, Server Load Balancing, that does the same for servers. While HSRP, VRRP, and CLBP all represent multiple physical routers to

CCNP Certification / BCMSN Exam Tutorial: QoS Service Types

CCNP Certification / BCMSN Exam Tutorial:  QoS Service Types

To earn your CCNP certification, you've got to know how the different QoS service types operate.  Learn the basics from Chris Bryant, CCIE #12933.:


To pass the CCNP exams, you’ve got to master Quality of Service, and the first step in doing so is knowing the differences between the different QoS types.

Now this being Cisco, we can't just have one kind of QoS! We've got best-effort delivery, Integrated Services, and Differentiated Services. Let's take a quick look at all three.

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

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

Just a few of the HSRP details you must know to earn your CCNA are configuring a MAC address for the virtual router.  Learn how to do so from Chris Bryant, CCIE #12933.

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

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

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

Route summarization requires a knowledge of binary conversion, as well as knowing how each protocol responds to summarization.  Learn how OSPF does so from Chris Bryant, CCIE #12933.

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 Certification / BCMSN Exam Tutorial: Getting Started With HSRP

CCNP Certification / BCMSN Exam Tutorial:  Getting Started With HSRP

HSRP seems simple enough, but there are a lot of options you need to know to pass the CCNP exams!  Learn how to get started with HSRP from Chris Bryant, CCIE #12933.


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.

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

BCMSN exam

To pass the BCMSN exam, you’ve got to know the ins and outs of VTP.  Review the basics and get ready for CCNP exam success with Chris Bryant, CCIE #12933.


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.

CCNA Certification Exam Tutorial: Cisco Switching Modes

CCNA Certification Exam Tutorial:  Cisco Switching Modes

An often-overlooked part of CCNA studies is learning the different modes a Cisco switch can run.  Learn these vital exam details from Chris Bryant, CCIE #12933.


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!

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

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CCNP BCMSN Exam Cram 2 (Exam Cram 642-811)

To pass the BCMSN exam, you’ve got to know the ins and outs of VTP.  Review the basics and get ready for CCNP exam success with Chris Bryant, CCIE #12933.

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 / MCSE / CCNP Certification: Creation Failure Work for You

CCNA / MCSE / CCNP Certification:  creation Failure Work for You

Failing an exam isn't the end of the world. It's happened to all of us, and you can make this failure work for you. Learn how from Chris Bryant, CCIE #12933.

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.


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

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

CCNA and CCNP candidates are often confused about why VLANs and VTP information is still present on a switch after the configuration is erased.  Learn why this happens and how to really delete VLAN information in this free tutorial from Chris Bryant, CCIE #12933.

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.

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CCNA / CCNP Home Lab lesson: assemble Your Cisco Home Lab

 At what time you're putting as one your Cisco home lab, you have a group of models to choose from!  Chris Bryant, CCIE #12933, shows you how he's built his CCNA / CCNP home labs and offers tips on purchasing your own Cisco routers.

Cisco Home Lab