It is common for students to get turned around, disoriented, and flustered when taking the CCNA exam. There are often complaints of ambiguity, poor wording, and obscure questions. While the problem of obscure questions can occur, most questions have subtleties testing your depth of understanding.
Learn how to interpret and distill exam questions effectively to pass the CCNA exam. New exam questions are comprised of multiple choice along with matching drag and drop type. It is important to become intuitive and learn to distill questions based on keywords and intent.
Each question will have keyword descriptors that will help you select the right answer. Some keyword examples include respond, install, factory, state, and forward. There is an intent with each question as well to test a concept. This could include the purpose and operation of a switch trunk for example, or route selection algorithm. The following are examples that explain question keywords, subtleties and identifying testing intent.
*All correct answers for each question are bolded.
Responding vs Operational
1. What command will verify that a router interface is operational and responding?
A. show running-config -> administrative only
B. show ip interface brief -> operational only
C. Telnet -> inconclusive
This question is testing your understanding of administrative and operational concepts for interfaces. The keyword responding is used here and that implies sending a packet to an interface and verifying that it is operational (up/up). The command show running-config is wrong. You are at the router and can only verify the interface is configured correctly. It is an administrative command that does not verify the interface is responding to arriving packets.
The question specifies you should verify the interface is responding and operational. You could have an Ethernet interface that is working fine and the problem is a downstream neighbor interface that is shutdown or filtering packets with an ACL.
The command show ip interface brief is wrong. You are at the router CLI issuing commands so there is no send/return of packets and you cannot confirm the interface is responding to arriving packets.
Telnet option is inconclusive since devices requires a Telnet configuration. You would not know if the problem was with the Telnet configuration (application layer), ACL filtering somewhere (application layer) or the physical interface.
Ping is the best answer. ICMP packets are sent to the interface and return with destination unreachable error or return pings received to confirm the router interface is operational.
2. What IOS commands will display the operational status of IPv4 configured interfaces? (select three)
A. show ip interface brief
B. show protocols
C. show interfaces
D. show running-config -> administrative only
E. ipconfig /all -> this is not an IOS command
F. show interfaces trunk -> Layer 2 interface only
This question asks for an IOS command that will display operational status of all configured Layer 3 network interfaces. The correct answers would display the operational status of active interfaces with an IP address, and must be Cisco IOS command only.
State vs Configuration
3. What IOS command will display OSPF adjacency state?
A. show ip ospf neighbor
B. show ospf interface -> wrong syntax
C. show ip ospf database -> wrong state information (database)
D. show running-config -> configuration only and not state
The show running-config command displays how an interface is configured, and not whether it is working correctly. You can have an interface configured so it is operational but not performing as expected. For example, you could have an operational trunk however it is dynamic trunking instead of the requested static trunking.
Select vs Install
4. What route is selected when multiple routes exist from different route sources to the same destination?
A. lowest administrative distance
B. lowest metric -> metric from same routing protocol with multiple routes
C. longest match prefix -> selects a route already installed in routing table
D. lowest cost metric -> from same routing protocol (OSPF) with multiple routes
This question is testing your knowledge of route selection algorithm. The keyword is select however install could have been used as well. You have to read further and notice routes to the same destination. Cisco algorithm considers routes with different prefix length as different destinations. The same algorithm would select and install a single route from among multiple routes with the same destination (prefix length). It is administrative distance that only affects what route is installed in routing table and not for best route (path) forwarding.
- same destination = OSPF 192.168.1.0/24 and EIGRP 192.168.1.0/24 –
lowest administrative distance rule selects EIGRP route to install in the routing table.
- different destination = 192.168.1.0/23, 192.168.1.0/24, 192.168.1.0/25 –
longest match rule selects 192.168.1.0/25 from the routing table for best path forwarding to destination.
Physical vs Logical vs Conceptual
It is important to distinguish between physical hardware, logical software configuration, and concepts that explain behavior. For example, neighbors are connected and communicate via network interfaces. There is a lookup in local routing table, and how they communicate is explained with the control plane model.
Factory / Unconfigured / Initial = Default Settings
Any reference to an initial or unconfigured device implies that Cisco default settings are enabled. The keyword factory is used as well to denote startup configuration erased for an initial configuration. Know the default settings for a Cisco device. In addition, protocols such as OSPF and trunking have defaults that are operational when no explicit configuration is made.
Bandwidth vs Cost vs Metric
Interface bandwidth is used in the context of physical link capacity while cost is a metric calculation performed by OSPF routing protocol. The bandwidth command can be used to change how routing protocols calculate metric, however physical link capacity is not affected.
Advantages vs Disadvantages
The common advantages keyword appears in many Cisco certification questions. There are foundational requirements (advantages) of network services that are universal. They include performance, scalability, security, redundancy, and ease of management. Select all answer/s that provide the advantages. EtherChannel for example has advantages of performance and redundancy.
The Matching Rule of Network Interfaces
It is a rule of thumb that interface configuration settings of directly connected neighbors must match on a variety of interface settings. This is helpful to know when answering questions and eliminating some options. Some examples include EtherChannel switch ports, trunk interface, and routing protocol neighbor adjacency.
- EtherChannel – switch port vlan membership, duplex, port mode, protocol.
- OSPF – hello timers, subnet, network type, area ID
Purpose vs Characteristics
Know the difference between purpose and characteristics for questions pertaining to network devices, services and protocols. Sometimes you have to select the best answer and identify the subtleties of why it is the best answer.
5. What is the primary purpose of a router?
A. traffic forwarding -> all devices do this
B. stateful packet inspection -> firewalls do this as well
C. traffic aggregation -> switches do this more than routers
D. per hop path selection
E. network access -> all devices do this
F. cloud connection -> routers also connect remote offices and internet
G. IP addressing -> hosts and servers write packets as well
This question requires that you to distinguish the primary role and function of a router. That includes similarities and differences among network devices to select only a single correct answer.
6. What is assigned to an OSPF Ethernet broadcast network? (select two)
A. loopback -> this is a logical IP interface and not a domain
D. multiple subnets -> domain broadcast is a single subnet only
E. Switched Virtual Interface (SVI) -> this is a logical IP interface associated with a VLAN
F. MAC address -> physical addresses assigned to individual hosts and devices
Originate vs Transit vs Forwarding
There is an operational planes model to explain the dynamics of data communications. The keyword originate refers to control plane packets only such as OSPF and STP that only start at a network device. It is forwarded only to a neighbor. There is also transit traffic referred to as data plane such as HTTP, that originate only from a host and transit a router. Transit traffic will traverse multiple hops. All traffic is forwarded by the network device to a next hop neighbor.
Read Question Carefully For Subtleties
7. What does a router do when no route exists to a destination?
A. drop packet
B. use the default route -> this is a route
C. send error message and retry -> partially true only since error message is sent
D. forward to nearest next hop neighbor -> no route exists to identify next hop
The question specifies that there is no route, so a default route does not exist either and packets are dropped immediately.
8. What two statements correctly describe Cisco INITIAL configuration settings?
A. CDP is enabled
B. DTP is enabled
C. management VLAN is disabled -> incorrect
D. VTY lines are enabled -> incorrect
Read this question carefully and do not miss that two (2) options exist and initial = default settings. For example you could hastily interpret question as – What statement is correct concerning Cisco configuration?
Additional Test-Taking Strategies
- The testing center will give you double-sided laminated paper at the beginning of the exam. Request 3-5 of them so you are not interrupting your exam.
- There is a 15-minute tutorial before the exam starts. Use that time to create your whiteboard notes. It is a collection of facts and figures that you have for quick reference. The online testing option provides a more difficult paint type digital whiteboard for students.
- Subnetting is a key aspect of the CCNA exam for a variety of questions. It is easy as well to make mistakes when converting between binary and decimal values. Write at least all class C subnets on paper when the exam starts. Include the subnetting table and binary table shown for quick conversions.
- Don’t burn time with a question you could only guess on. Start eliminating wrong options, take an educated guess, and then move on to the next question.
- Read each question a couple of times carefully and notes any keywords and intent.
- Do not click Next until you are satisfied with your answer and ready for the next question. There is no review allowed or navigation permitted to a previous question.
- Do not waste time considering answers from any previous questions. There is no back button or end of test question review with CCNA exam.
- Cisco recommends not spending more than 7-10 minutes on any performance-based lab.