I love interesting problems that we face when studying for our CCIEs. Especially fun are those that come from an unusual behavior of protocols.
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In this ongoing series here at blog.ipexpert.com, we are going to answer the most common questions CCIE instructors hear. Here is the latest:

Question: Am I penalized for over-configuration in the lab exam?

Answer: This is another one of those great questions, especially when you consider the fact that the grading for the lab exam is quite complex. Depending on what track you are discussing, the lab is graded by a computer script, a human, or a combination of both. Given this fact, students begin to suspect that the grading is some mysterious “black art”, that might harshly penalize for the slightest deviation from the proctor’s expectations with a task.

I like to answer this question for students with an example. Say you get the task below:

Sample Task 1 – Switching

1.3 Trunking

Create a standards-based trunk between SW1 and SW4 according to the Layer 2 diagram provided.

2 pts

I recommend that students ask themselves the question here –  how would the proctor write a script to grade this task? I think they would issue the SHOW INTERFACE TRUNK command on each device. In your mind, run through the parameters that must exist.

• Correct two devices
• Correct two interfaces
• UP/UP status
• 802.1Q trunk established

If these parameters are met – you just achieved the 2 pts.

Here are three different configurations (from just one of the two devices) that get the full two points.

Solution 1

switchport trunk encapsulation dot1q
switchport mode trunk

Solution 2

switchport trunk encapsulation dot1q
switchport mode trunk
switchport nonegotiate

Solution 3

switchport trunk encapsulation dot1q
switchport mode trunk
switchport nonegotiate
switchport trunk allowed-vlan 100,200,300,400,500,501,502

Always ask yourself two questions:

1. Could this additional configuration I am about to add help me gain these points?
2. Could this additional configuration I am about to add potentially cost me here or elsewhere in the lab?

If your answers are YES and NO respectively, then you can certainly consider this “additional” configuration. Notice that Solution 3 comes very close to a NO and YES answer respectfully and should be frowned upon as a result.

Another great rule of thumb in this regard – “do what they ask for, nothing more, nothing less!”

Anthony Sequeira CCIE, CCSI
Twitter: @compsolv
Facebook: http://www.facebook.com/compsolv

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It is true that one does not need many debug commands in order to survive the CCIE Routing and Switching Lab Exam. Sure, perhaps a debug ip rip command could prove very important for that pathetic little routing protocol, but surely we will not be doing anything near the debugging we tend to do when we are first learning our protocols.

For me another important exception to the “no to little debug rule” in the lab exam is debug ip routing. This powerful debug is part of my plan to solving the lab if we have to do some nasty complex redistribution.

You see in the context of the CCIE R&S Lab Exam, this command will be harmless. Even in the event we do have routing loops or feedback, there will not be enough routes having an issue to cause problems for the console access of our devices. In fact, is there is an issue like this caused by redistribution (or some other mechanism), the command makes this instability very, very obvious.

When something is going awry with your underlying routing table, this command is so powerful for pointing it out to you. Examine the example below where a “flapping” interface is causing problems:

Router#debug ip routing
IP routing debugging is on
Router#*Mar  1 00:02:59.115: RT: delete route to 10.10.10.0 via 1.1.1.2, eigrp metric [90/409600]
*Mar  1 00:02:59.115: RT: no routes to 10.10.10.0
*Mar  1 00:02:59.119: RT: NET-RED 10.10.10.0/24
*Mar  1 00:02:59.119: RT: delete subnet route to 10.10.10.0/24
*Mar  1 00:02:59.119: RT: NET-RED 10.10.10.0/24
*Mar  1 00:02:59.123: RT: delete network route to 10.0.0.0
*Mar  1 00:02:59.123: RT: NET-RED 10.0.0.0/8
*Mar  1 00:03:06.247: RT: add 10.10.10.0/24 via 1.1.1.2, eigrp metric [90/409600]
*Mar  1 00:03:06.251: RT: NET-RED 10.10.10.0/24
*Mar  1 00:03:43.907: RT: delete route to 10.10.10.0 via 1.1.1.2, eigrp metric [90/409600]
*Mar  1 00:03:43.911: RT: no routes to 10.10.10.0
*Mar  1 00:03:43.911: RT: NET-RED 10.10.10.0/24
*Mar  1 00:03:43.911: RT: delete subnet route to 10.10.10.0/24
*Mar  1 00:03:43.915: RT: NET-RED 10.10.10.0/24
*Mar  1 00:03:43.915: RT: delete network route to 10.0.0.0
*Mar  1 00:03:43.915: RT: NET-RED 10.0.0.0/8
*Mar  1 00:03:50.879: RT: add 10.10.10.0/24 via 1.1.1.2, eigrp metric [90/409600]
*Mar  1 00:03:50.883: RT: NET-RED 10.10.10.0/24

If everything is stable with your underlying routing table, you will not have anything like the above output. With certain protocols like BGP, you will see this passive little message pop up periodically that has to do with scanning of the table. It is harmless and can be ignored.

I like to turn this command on all of my devices in the Configuration section before I do any redistribution. I will then leave it on for the remainder of the lab, only removing it at the end of the lab before I do my final saves and leave the testing center for the day. Why leave it on? Well, it will be a nice obvious visual indicator should I break something later in the day - especially during Security configurations.

Anthony Sequeira CCIE, CCSI
Twitter: @compsolv
Facebook: http://www.facebook.com/compsolv

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I think one of the reasons there are such struggles with the CCIE R&S Lab Exam is the glaring lack of excellent CCIE R&S Written Prep materials. Before you think I sound like a jerk that is bashing the products of others, understand that I fully recognize that I am guilty as well. In the past, I have created training products for this niche, but these products were far too focused on one thing – passing the Written Exam.

I am excited to announce that a new and exciting live online product is coming from IPexpert that will be a revolution for this important level of study. For the convenience of students, this course will run evenings (8 to 10 PM EST USA) two nights a week. We are looking to start it in November 2011. Get ready, folks. This will be an event you will not want to miss. Stay tuned for more details.

Anthony Sequeira CCIE, CCSI
Twitter: @compsolv
Facebook: http://www.facebook.com/compsolv

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You are in the CCIE R&S Lab Exam, and you read the following:

8.0 Quality of Service (QoS)

8.1 Configure SW1, and its port Fa0/12, so that it is optimized for VoIP traffic if that traffic is sent from a genuine Cisco IP Phone. Use the minimal number of commands in your configuration.

2 pts

Remember the song from the 1990’s by C+C and the Music Factory entitled “Things That Make You Go Hmmmmm”? You might be having one of those moments now. We need to optimize the switch and the port for this VoIP traffic, and we only get two measly points!?!?

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