Module 12 Pre-Assessment

What are two reasons to create a network baseline? (Choose two.)

• to determine what kind of equipment to implement

• to evaluate security vulnerabilities in the network

• to identify future abnormal network behavior

• to design a network according to a proper model

• to determine if the network can deliver the required policies

Answer explanation

A network baseline is created to provide a comparison point, at the time that the network is performing optimally, to whatever changes are implemented in the infrastructure. A baseline helps to keep track of the performance, to track the traffic patterns, and to monitor network behavior.

A computer can access devices on the same network but cannot access devices on other networks. What is the probable cause of this problem?

• The cable is not connected properly to the NIC.

• The computer has an invalid IP address.

• The computer has an incorrect subnet mask.

• The computer has an invalid default gateway address.

Answer explanation

The default gateway is the address of the device a host uses to access the Internet or another network. If the default gateway is missing or incorrect, that host will not be able to communicate outside the local network. Because the host can access other hosts on the local network, the network cable and the other parts of the IP configuration are working.

In which step of gathering symptoms does the network engineer determine if the problem is at the core, distribution, or access layer of the network?

• Document the symptoms.

• Determine the symptoms.

• Gather information.

• Determine ownership.

• Narrow the scope.

Answer explanation

In the "narrow the scope" step of gathering symptoms, a network engineer will determine if the network problem is at the core, distribution, or access layer of the network. Once this step is complete and the layer is identified, the network engineer can determine which pieces of equipment are the most likely cause.

Refer to the exhibit. Why are routers R1 and R2 not able to establish an OSPF adjacency?​

• The router ID values are not the same in both routers.

• The serial interfaces are not in the same area.

• The process numbers are not the same in both routers.

• A backbone router cannot establish an adjacency with an ABR router.

Answer explanation

On router R1, the network 192.168.10.0/30 is defined in the wrong area (area 1). It has to be defined in area 0 in order to establish adjacency with router R2, which has the network 192.168.10.0/30 defined in area 0.

When is the most appropriate time to measure network operations to establish a network performance baseline?

• at random times during a 10 week period, so that abnormal traffic levels can be detected

• during quiet vacation periods, so that the level of non-data traffic can be determined

• whenever high network use is detected, so that how the network performs under stress can be monitored

• at the same time each day across a set period of average working days, so that typical traffic patterns can be established

Answer explanation

The purpose of establishing a network performance baseline is to provide a reference of normal or average network use to enable data traffic anomalies to be detected and then investigated. Network operations that are not average, or are not normal, cannot be used to establish a network performance baseline.

What is the principle that is applied when a network technician is troubleshooting a network fault by using the divide-and-conquer method?

• Testing is performed at all layers of the OSI model until a non-functioning component is found.

• Once it is verified that a component in a particular layer is functioning properly, testing can then be performed on any other layer.

• Testing is performed at Layer 7 and at Layer 1, then at Layers 6 and 2, and so on, working towards the middle of the stack until all layers are verified as operational.

• Once it is verified that components in a particular layer are functioning properly, it can then be assumed that components in the layers below it are also functional.

Answer explanation

The nature of the OSI and TCP/IP layered models is that upper layers are dependent on lower layers. So when troubleshooting, if a particular layer is found to be working correctly then it can be assumed that all layers below it are also functioning correctly.

Refer to the exhibit. A user has configured a NIC on the PC as shown but finds that the PC is unable to access the Internet. What is the problem?

• The preferred DNS address is incorrect.

• There should not be an alternate DNS server.

• The settings were not validated upon exit.

• The default gateway address is incorrect.

Answer explanation

In order for a computer to communicate outside its network, it must have a valid default gateway configured.This address cannot be the same as the IP address of the computer.

Which troubleshooting tool would a network administrator use to check the Layer 2 header of frames that are leaving a particular host?

• protocol analyzer

• baselining tool

• knowledge base

• CiscoView

Answer explanation

A protocol analyzer such as Wireshark is capable of displaying the headers of data at any OSI Layer.

Refer to the exhibit. A network engineer configured an ACL preventing Telnet and HTTP access to the HQ web server from guest users in the Branch LAN. The address of the web server is 192.168.1.10 and all guest users are assigned addresses in the 192.168.10.0/24 network. After implementing the ACL, no one can access any of the HQ servers. What is the problem?

• Inbound ACLs must be routed before they are processed.

• The ACL is implicitly denying access to all the servers.

• Named ACLs require the use of port numbers.

• The ACL is applied to the interface using the wrong direction.

Answer explanation

Both named and numbered ACLs have an implicit deny ACE at the end of the list. This implicit deny blocks all traffic.

Refer to the exhibit. A network administrator has configured OSPFv2 on the two Cisco routers as shown. PC1 is unable to connect to PC2. What should the administrator do first when troubleshooting the OSPFv2 implementation?

• Test Layer 3 connectivity between the directly connected routers.

• Turn off OSPFv2.

• Disconnect the serial link between router R1 and R2.

• Implement the network 192.168.255.0 0.0.0.3 area 0 command on router R1.

Answer explanation

A prerequisite for OSPFv2 neighbor relationships to form between two routers is Layer 3 connectivity. A successful ping confirms that a router interface is active and may be able to form an OSPF neighbor adjacency.