Are you a CCNP or CCIE student looking to challenge your perfect knowledge of Catalyst switchport commands?
Take the latest SWITCH Command Recall exam by clicking the link below. Good luck – and let us know how you scored in the comments area of this post.
Remember to read, AND TYPE, very carefully! I failed my first attempt due to just plain sloppiness. 
SWITCH Command Recall Exam – L2/L3 Ports
In the first part of this series, we subdivided the processes of EIGRP into four discrete steps, and detailed troubleshooting the first two. This is taken from the 5-Day CCNP bootcamp:
Let us now discuss path selection and maintenance troubleshooting.
We should all remember that we can view the topology table of EIGRP with the command show ip eigrp topology. Here we can see the successor routes (these are the best routes that are placed in the routing table) and we can see the second best routes, the feasible successor routes. These feasible successor routes are the key to the lightening fast convergence that EIGRP can offer us. When a speaker loses its successor, it can quickly install a feasible successor route in its place.
We need to remember the important rule of feasible successors. The advertised distance of the proposed feasible successor must be less than the feasible distance of the current successor route. This is actually a loop prevention mechanism.
Another big gotcha when it comes to path selection in EIGRP is the configuration of variance to unequal cost load balance. I can remember fighting with this in an INE practice lab long ago when I was preparing for the exam. Something I had no idea of back then…in order to be considered for the unequal load balancing, the alternate paths must be feasible successors! Older editions of CCNP courses never thought to tell us that little nugget!
We should be careful when modifying bandwidth to effect path selection. Cisco gave us delay for this purpose. Modifying the bandwidth can starve EIGRP updates of bandwidth to use. Remember, by default, EIGRP will only use 50% of an interface’s bandwidth. We can control this with the command ip bandwidth percent eigrp.
For table maintenance, show ip eigrp topology is critical. Note that in this table, passive is what we want to see. Active indicates there is not a feasible successor and neighbors are being queried for an alternative path. SIA log messages indicate a Stuck in Active issue. Here the router is not receiving a reply to queries. The most common reasons this can occur:
When it comes to table maintenance, another excellent troubleshooting command is show ip eigrp topology summary. This command displays the total number of routes in the topology table and the total number of queries the router is waiting on responses for. It also shows a quiescent interface field that shows which interface have no outstanding packets to be sent or acknowledged.
Some of our favorite EIGRP verification commands:
So many students have written me excited for the upcoming Cisco Certified Design Associate (CCDA) 5 day online bootcamp. In this blog post I want to provide everyone with a preview of some of the hugely valuable content in this course.
Early in the week of the event, we review a network health checklist from Cisco Systems. We take this one step further during the bootcamp and show you how to actually obtain these measurements without breaking your budget:
A common question for the CCNA Voice candidate is – “Just how can we translate our analog voice waveform into the digitized form that is required for Voice over IP transmission through the converged network?” These active reading questions tell the story – enjoy!
Me Singing in the Shower!
Questions Only
In its natural form, what signal type is the human voice?
To send voice as a series of zeros and ones is known as what type of encoding?
Converting analog voice into digital data begins with taking “snapshots” of voice very frequently. This is called what?
If you sample voice too infrequently, the listener might hear a different sound. This is called what?
What is the reason that you would not want to oversample voice?
What theorem teaches that the sample rate needs to be twice as high as the highest frequency being sampled?
Based on the Nyquist Theorem, how often should we sample voice?
What is the initial process of voice sampling called?
What is the process of taking PAM amplitudes and assigning them a number?
What type of scale is used in voice quantization?
Rounding off during quantization can cause a “hiss” on the line. This is called what?
When is quantization error more noticeable?
What approach to the quantization logarithmic scale is commonly used in North America?
What approach to the quantization logarithmic scale is commonly used outside North America?
If VoIP equipment connects from different countries, what quantization logarithmic scale is used?
What is the breakdown of the 8 bits in a voice sample?
When considering voice sampling only- how much bandwidth is required to send voice and how is the value arrived at?
The process of encoding and decoding a wave form to save bandwidth is accomplished by what type of technology?
What type of codec does not actually compress the waveform and what is an example?
What type of codec sends the difference in the current sample versus the previous sample and what is an example?
What type of codec dynamically builds a codebook based on speech patterns and what is an example?
What is the most popular codec in the Cisco VoIP environment for sending voice over the WAN and why?
What is the bandwidth for a voice call required under the G.711 codec?
What is the bandwidth required for a voice call under the G.729 codec?
What type of codec is very similar to CS-ACELP but uses a smaller codebook and what is an example?
What are the bandwidth and delay characteristics of LDCELP?
What codec is typically used in the LAN in a Cisco VoIP environment?
What variation of G.729 uses a less complex algorithm?
What variation of G.729 enables VAD?
What is VAD?
What are four other factors that impact the size of a voice packet?
What VoIP quality measurement uses a trained ear to rate quality on a scale of 1 to 10?
What quality measurement digitally measures the difference in the original signal and the signal after it passes through the codec?
What variation of PSQM attempts to match the measurement with MOS?
Calculating the number of telephone calls during the busiest time of day is referred to as what?
What is an Erlang?
What is the formula for calculating the number of call minutes a corporate phone system uses during the busiest hour of the day?
What is the percentage of call to reject during the busiest hour of the day referred to as?
Questions and Answers
In its natural form, what signal type is the human voice?
Analog
To send voice as a series of zeros and ones is known as what type of encoding?
Binary
Converting analog voice into digital data begins with taking “snapshots” of voice very frequently. This is called what?
Sampling
If you sample voice too infrequently, the listener might hear a different sound. This is called what?
Aliasing
What is the reason that you would not want to oversample voice?
Requires too much bandwidth
What theorem teaches that the sample rate needs to be twice as high as the highest frequency being sampled?
The Nyquist Theorem
Based on the Nyquist Theorem, how often should we sample voice?
Every 125 ms
What is the initial process of voice sampling called?
PAM (Pulse Amplitude Modulation)
What is the process of taking PAM amplitudes and assigning them a number?
Quantization
What type of scale is used in voice quantization?
Logarithmic
Rounding off during quantization can cause a “hiss” on the line. This is called what?
Quantization error
When is quantization error more noticeable?
At lower volumes
What approach to the quantization logarithmic scale is commonly used in North America?
Mu-Law
What approach to the quantization logarithmic scale is commonly used outside North America?
a-Law
If VoIP equipment connects from different countries, what quantization logarithmic scale is used?
a-Law
What is the breakdown of the 8 bits in a voice sample?
1 Polarity Bit; 3 Segment Bits; and 4 Step Bits
When considering voice sampling only- how much bandwidth is required to send voice and how is the value arrived at?
8000 samples per second * 8 bits per sample = 64 Kbps
The process of encoding and decoding a wave form to save bandwidth is accomplished by what type of technology?
A Codec
What type of codec does not actually compress the waveform and what is an example?
Pulse Code Modulation (PCM); an example is G.711
What type of codec sends the difference in the current sample versus the previous sample and what is an example?
Adaptive Differentiated PCM (ADPCM); an example is G.726
What type of codec dynamically builds a codebook based on speech patterns and what is an example?
Conjugate Structure Algebraic Code Excited Linear Prediction (CS-ACELP); G.729 is an example
What is the most popular codec in the Cisco VoIP environment for sending voice over the WAN and why?
G.729; decent quality with lower bandwidth requirements
What is the bandwidth for a voice call required under the G.711 codec?
64 Kbps
What is the bandwidth required for a voice call under the G.729 codec?
8 Kbps
What type of codec is very similar to CS-ACELP but uses a smaller codebook and what is an example?
Low-Delay Conjugate Excited Linear Prediction (LDCELP); G.728
What are the bandwidth and delay characteristics of LDCELP?
It reduces delay, but at the cost of higher bandwidth
What codec is typically used in the LAN in a Cisco VoIP environment?
G.711
What variation of G.729 uses a less complex algorithm?
G.729a
What variation of G.729 enables VAD?
G.729b
What is VAD?
Voice Activity Detection – devices will not send “the sound of silence” with VAD
What are four other factors that impact the size of a voice packet?
Media, Tunneling, Header Compression, Codec used
What VoIP quality measurement uses a trained ear to rate quality on a scale of 1 to 10?
Mean Opinion Score (MOS)
What quality measurement digitally measures the difference in the original signal and the signal after it passes through the codec?
PSQM (Perceptual Speech Quality Measurement)
What variation of PSQM attempts to match the measurement with MOS?
PESQ (Perceptual Evaluation of Speech Quality)
Calculating the number of telephone calls during the busiest time of day is referred to as what?
Traffic Engineering
What is an Erlang?
One solid hour of phone usage
What is the formula for calculating the number of call minutes a corporate phone system uses during the busiest hour of the day?
[Monthly_Call_Minutes/22] * .15
What is the percentage of call to reject during the busiest hour of the day referred to as?
GOS (Grade of Service)
For the latest Video Blog – simply click the link below:
This Video Blog demonstrates and discusses uses for this powerful rack rental tool.
During this video I mentioned that it is now possible to view and download your saved configs, but I forgot to show from where. The location is shown below. Enjoy!
Enjoy this Video Blog that walks you through subscribing to the blog.ine.com site in Microsoft Outlook.
Check out the Video Companion for Volume 2 for several hours of added content. Join Keith Barker and myself, Anthony Sequeira, as we walk you through our CCIE-level approaches to the new Trouble Tickets of the Volume 2 workbook.
Enjoy!
Check out the Video Companion for Volume 2 for several hours of added content. Join Keith Barker and myself, Anthony Sequeira, as we walk you through our CCIE-level approaches to the new Trouble Tickets of the Volume 2 workbook.
Enjoy!
The best-selling Volume 2 practice lab workbook from INE has been updated with new, 2-hour Troubleshooting sections that mirror the actual Cisco Lab Exam. Labs 1 through 3 are published now to member accounts. More are on the way!
Do you want to watch Keith Barker solve the Lab 1 TS section? Check out the updated Interactive Video Companion! I will be demonstrating my approach to Lab 2 in that product next week.
Enjoy the updates everyone, and as always, thank you so much for choosing INE.
Try these questions on for size! Learn all this and much more in the new QoS class – woohoo!
1. Based on the following configuration, what traffic will be policed?
class-map C_MUSIC
match protocol kazaa2
match protocol napster
!
class-map match-any C_WEB
match protocol http
match class-map C_MUSIC
!
policy-map P_WEB
class C_WEB
police 64000
!
interface serial 0/0
service-policy output P_WEB
A. All Kazaa version 2 traffic is policed
B. All Napster traffic is policed
C. All web traffic is policed
D. All Kazaa version 2, Napster, and web traffic is policed
E. No traffic is policed
Answer:
C
Explanation:
The C_MUSIC class-map does not specify the match-any or match-all option. The default is match-all. Therefore, for traffic to be classified in the C_MUSIC class-map, a packet would simultaneously have to be a Kazaa version 2 packet and a Napster packet, which isn’t possible.
The C_WEB class-map uses the match-any option, meaning that traffic will be classified in this class-map if it is HTTP traffic or if it is traffic that was classified in the C_MUSIC class-map. Since, no traffic will be classified in the C_MUSIC class-map, as described above, the only traffic that will be classified by the C_WEB class-map is HTTP traffic.
The policy-map P_WEB is configured to police (i.e. rate limit) traffic classified by the C_WEB class-map to a bandwidth of 64 kbps. (NOTE: The default conform-action is transmit, and the default exceed-action is drop.) Since only HTTP (i.e. web) traffic is matched by the C_WEB class-map, web traffic is the only traffic that is policed.
2. You are configuring a Cisco Catalyst 3560 switch port to trust CoS markings if, and only if, the marking originated from a Cisco IP Phone. In an attempt to perform this configuration, you enter the mls qos trust device cisco-phone command. However, your configuration does not seem to be working properly. Why is the switch not trusting CoS markings coming from an attached Cisco IP Phone?
A. A Cisco Catalyst 2950 switch supports the mls qos trust device cisco-phone command, but the Cisco Catalyst 3560 does not support this command
B. The mls qos trust cos command is missing
C. The mls qos trust extend command is missing
D. The mls qos cos 5 command is missing
E. The PC attached to the phone is overriding the CoS markings
Answer:
B
Explanation:
A Cisco Catalyst 2950 switch port can be configured to trust Class of Service (CoS) markings, Differentiated Services Code Point (DSCP), or CoS markings originating from a Cisco IP Phone. The switch port can detect that a CoS marking is coming from a Cisco IP Phone via the Cisco Discovery Protocol (CDP). The mls qos trust device cisco-phone command does indeed tell the switch to trust a marking if, and only if, the marking comes from a Cisco IP Phone. However, the mls qos trust device cisco-phone command by itself does not tell the switch port which marking (i.e. CoS or DSCP) coming from the Cisco IP Phone to trust. Therefore, the mls qos trust cos command is also required.
3. You administer a network that transports both voice and interactive video traffic. Since these traffic types are both latency-sensitive, you decide to implement the following configuration. Which statement is true regarding the configuration?
class-map C_VOICE
match protocol rtp audio
!
class-map C_VIDEO
match protocol rtp video
!
policy-map P_HIGH_PRIORITY
class C_VOICE
priority percent 15
class C_VIDEO
priority percent 35
class class-default
fair-queue
!
interface serial 0/0
service-policy output P_HIGH_PRIORITY
A. The configuration results in three queues, one for the C_VOICE class, one for the C_VIDEO class, and one queue for the class-default class
B. The configuration results in two queues, one priority queue and one queue for the class-default class
C. The class-default class uses FIFO as its queuing mechanism for traffic flows within its queue
D. The two priority queues use WFQ for queuing traffic within those queues
Answer:
B
Explanation:
While priority treatment (i.e. LLQ treatment) can be assigned to more than one class-map, an interface only has one priority queue. Therefore, in the above configuration, traffic classified in the C_VOICE and C_VIDEO class-maps shares the same priority queue. A second queue contains traffic classified in the class-default class-map. Therefore, the configuration only results in two queues, one shared priority queue and one queue for the class-default class. On most models of routers, only the class-default queue can be configured to use WFQ queuing for flows within the queue, while other queues use FIFO queuing for traffic within those queues.
4. CB-WRED is configured using the random-detect command. Which two of the following statements are true concerning the random-detectcommand? (Choose 2)
A. The random-detect command cannot be issued for the class-default class.
B. The random-detect command cannot be issued for the priority class(es).
C. The random-detect command must be issued in conjunction with the bandwidth command (with the exception of the class-default class).
D. The random-detect command should be issued in conjunction with the priority command.
Answer:
B, C
Explanation:
Weighted Random Early Detection (WRED) is effective for TCP flows, because WRED can cause some TCP flows to enter TCP slow start. When configuring class-based WRED (i.e. CB-WRED), the random-detect command is issued in policy-map-class configuration mode. While the random-detect command can be used with the class-default class, random-detect cannot be issued in policy-map-class configuration mode for a class configured with the priority keyword. Also, with the exception of the class-default class, the random-detect command must be issued along with the bandwidth command.
5. Consider the following configuration:
class-map TRANSACTIONAL
match protocol http
!
policy-map CBPOLICING
class TRANSACTIONAL
police 128000 conform-action set-dscp-transmit af11 exceed-action set-dscp-transmit af13 violate-action drop
!
interface serial 0/1
service-policy input CBPOLICING
What type of class-based policing configuration is represented by this configuration?
A. Single rate, single bucket
B. Single rate, dual bucket
C. Dual rate, single bucket
D. Dual rate, dual bucket
Answer:
B
Explanation:
Cisco IOS supports single rate, single bucket; single rate, dual bucket; and dual rate, dual bucket policers. With a single rate policer, only a committed information rate (CIR) is specified, as in this question. With a dual rate policer, both a CIR and a peak information rate (PIR) are specified. Also, a single rate policer is a single bucket policer, unless the violate action is specified. If the violate action is specified, as it is in this question, the single rate policer uses two buckets, a Bc bucket and a Be bucket. However, a dual rate policer always uses two buckets, one bucket to transmit traffic at the CIR and one bucket to transmit traffic at the PIR.
6. You configure CB-Shaping by issuing the command shape peak 8000 2000 2000. This configuration shapes to what peak rate?
A. 4000 bps
B. 8000 bps
C. 16000 bps
D. 32000 bps
Answer:
C
Explanation:
In the syntax, the 8000 represents the Committed Information Rate (CIR). The first 2000 is the Committed Burst (Bc), and the second 2000 is the Excess Burst (Be). When configuring CB-Shaping, you can either shape to “average” or shape to “peak.” When shaping to average, traffic rates don’t exceed the CIR. However, when shaping to peak, traffic rates can burst above the CIR, while some of that excess traffic could be dropped by the service provider. When shaping to peak, the peak shaping rate is calculated by the formula:
peak_rate = CIR * (1 + Be/Bc)
In this example: peak_rate = 8000 * (1 + 2000/2000) = 16,000 bps. Note that if the Bc and Be values are calculated by IOS rather than being statically configured, Bc will always equal Be, which means that the peak rate will be twice the CIR.
7. You are configuring Multilink PPP (MLP) as your Link Fragmentation and Interleaving (LFI) mechanism for a WAN link. Identify the correct statements regarding the configuration of MLP. (Choose 2)
A. The configuration of Multilink PPP requires at least two physical links (e.g. two serial interfaces)
B. The IP address is removed from any serial interface that makes up the MLP bundle
C. Any policy-map that was previously assigned to a physical interface should be reassigned to the multilink interface, that the physical interface is associated with, in order for the policy to take effect
D. The virtual multilink interface does not use an IP address. Rather, it uses the IP unnumbered feature which allows the multilink interface to share an IP address with the multilink bundle member that has the highest IP address
Answer:
B, C
Explanation:
Multilink PPP (MLP) is a Link Fragmentation and Interleaving (LFI) mechanism for PPP links. Interestingly, even though the term “multilink” is in the title of this mechanism, MLP can be configured on a single link. Specifically, a virtual multilink interface is created. Then, one or more physical interfaces are added as members of a multilink bundle, all of which act as the single multilink interface. As a result, the virtual multilink interface is assigned an IP address, while the one or more physical interface member(s) do not have an IP address. Additionally, since the packets are logically transmitted over the virtual multilink interface, in order to apply a policy-map to the traffic using the virtual interface, the service-policy command should be applied to the virtual multilink interface, as opposed to the member interfaces.
