CCNA / CCNP Cisco Certification Exam: Frame Relay Encapsulation Types

Frame Relay encapsulation seems simple enough, but for your CCNA and CCNP exams, you've got to know vital details that are often overlooked.  Learn these details from Chris Bryant, CCIE #12933.

 CCNA / CCNP Cisco Certification Exam:  Frame Relay Encapsulation Types

CCNA / CCNP Cisco Certification Exam: Caller ID Screening And Callback

To pass Cisco certification exams, you have to know more than one way to do things.  Learn another method of configuring ISDN callback from Chris Bryant, CCIE #12933.

CCNA / CCNP Cisco Certification Exam:  Caller ID Screening And Callback

CCNA / CCNP Cisco Certification Exam: Cabling Your Home Lab

Putting together a Cisco home lab is a great idea, but sometimes choosing the right cabling can be a little confusing.  Learn the details from Chris Bryant, CCIE #12933.

CCNA / CCNP Cisco Certification Exam: Attending A Video Boot Camp

Not every CCNA and CCNP candidate has thousands of dollars to spend on a boot camp.  Learn how to get the same quality training for less money and travel from Chris Bryant, CCIE #12933.

CCNA / CCNP Cisco Certification Exam:  Attending A Video Boot Camp

When you're studying for the CCNA and CCNP exams, you've got a lot of different choices when it comes to training.   One popular choice is choosing one of the many "boot camps" and five-day in-person courses that are out there.  I've taught quite a few of these, and while many of them are good, they do have drawbacks. 

CCNP Certification: How And Why To Build An Etherchannel

Etherchannels are in use all over the world, as well as on your CCNA and CCNP exams.  Learn how to build and support an EC in this tutorial from Chris Bryant, CCIE #12933.

 CCNP Certification: How And Why To Build An Etherchannel

CCNA and CCNP candidates are well-versed in Spanning-Tree Protocol, and one of the great things about STP is that it works well with little or no additional configuration. There is one situation where STP works against us just a bit while it prevents switching loops, and that is the situation where two switches have multiple physical connections.

Introduction To BGP Attributes|Cisco CCNA / CCNP Certification

BGP is one of the most complex topics you’ll tackle in your CCNP studies, but if you break it down to the fundamentals, you’ll pick it up quickly.  Chris Bryant, CCIE #12933, has written this free BGP tutorial on BGP attributes to help you do master BGP and pass the exams!

 Introduction To BGP Attributes|Cisco CCNA / CCNP Certification

 

BGP is one of the most complex topics you'll study when pursuing your CCNP, if not the most complex. I know from personal experience that when I was earning my CCNP, BGP is the topic that gave me the most trouble at first. One thing I keep reminding today's CCNP candidates about, though, is that no Cisco technology is impossible to understand if you just break it down and understand the basics before you start trying to understand the more complex configurations.

Cisco CCNA / CCNP / BCMSN Exam Review: Trunking And Trunking Protocols

You've got to know the details of trunks and trunking protocols to earn your CCNA and CCNP.  Learn these details from Chris Bryant, CCIE #12933.

Cisco CCNA / CCNP / BCMSN Exam Review:  Trunking And Trunking Protocols

To earn your CCNA or CCNP certification, you've got to understand the basics of trunking.  This isn't just a CCNA topic - you must have an advanced understanding of trunking and etherchannels to pass the BCMSN exam and earn your CCNP as well.  Before we address those advanced topics, though, you need to master the fundamentals!

Get Cisco CCNA / CCNP Certification|OSPF E2 vs. E1 Routes

When preparing for CCNA and CCNP success, you’ve got to know the many details of OSPF.   Learn about these two vital OSPF route types and how they differ from each other in this free tutorial from Chris Bryant, CCIE #12933.

Get Cisco CCNA / CCNP Certification|OSPF E2 vs. E1 Routes

OSPF is a major topic on both the CCNA and CCNP exams, and it's also the topic that requires the most attention to detail.  Where dynamic routing protocols such as RIP and IGRP have only one router type, a look at a Cisco routing table shows several different OSPF route types.
R1#show ip route

CCNP Certification Exam |Floating Static Routes on cisco

Cisco CCNA  / CCNP Certification Exam Tutorial:  Floating Static Routes

Knowing when and how to configure floating static routes is an important skill on your Cisco certification exams, as well as working in real-world networks.  Learn all about floating static routes from Chris Bryant, CCIE #12933.

CCNP Certification Exam |Floating Static Routes on cisco

 

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!

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!

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