2021 Apr 100-105 free exam questions

Q51. - (Topic 7) 

Which routing protocol has the smallest default administrative distance? 

A. IBGP 

B. OSPF 

C. IS-IS 

D. EIGRP 

E. RIP 

Answer:

Explanation: http://www.cisco.com/c/en/us/support/docs/ip/border-gateway-protocol-bgp/15986-admin-distance.html Default Distance Value TableThis table lists the administrative distance default values of the protocols that Cisco supports: 

Route Source Default Distance Values 

Connected interface 0 Static route 1 Enhanced Interior Gateway Routing Protocol (EIGRP) summary route 5 External Border Gateway Protocol (BGP) 20 Internal EIGRP 90 IGRP 100 OSPF 110 Intermediate System-to-Intermediate System (IS-IS) 115 Routing Information Protocol (RIP) 120 Exterior Gateway Protocol (EGP) 140 On Demand Routing (ODR) 160 External EIGRP 170 Internal BGP 200 Unknown* 


Q52. - (Topic 3) 

After the network has converged, what type of messaging, if any, occurs between R3 and R4? 

A. No messages are exchanged 

B. Hellos are sent every 10 seconds. 

C. The full database from each router is sent every 30 seconds. 

D. The routing table from each router is sent every 60 seconds. 

Answer:

Explanation: 

HELLO messages are used to maintain adjacent neighbors so even when the network is converged, hellos are still exchanged. On broadcast and point-to-point links, the default is 10 seconds, on NBMA the default is 30 seconds. Although OSPF is a link-state protocol the full database from each router is sent every 30 minutes (not seconds) therefore, C and D are not correct. 


Q53. - (Topic 3) 

Scenario 

Refer to the topology. Your company has decided to connect the main office with three other remote branch offices using point-to-point serial links. 

You are required to troubleshoot and resolve OSPF neighbor adjacency issues between the main office and the routers located in the remote branch offices. 

An OSPF neighbor adjacency is not formed between R3 in the main office and R6 in the Branch3 office. What is causing the problem? 

A. There is an area ID mismatch. 

B. There is a PPP authentication issue; the username is not configured on R3 and R6. 

C. There is an OSPF hello and dead interval mismatch. 

D. The R3 router ID is configured on R6. 

Answer:

Explanation: 

Using the show running-config command we see that R6 has been incorrectly configured with the same router ID as R3 under the router OSPF process. 


Q54. - (Topic 3) 

Some routers have been configured with default routes. What are some of the advantages 

of using default routes? (Choose two) 

A. They establish routes that will never go down. 

B. They keep routing tables small. 

C. They require a great deal of CPU power. 

D. They allow connectivity to remote networks that are not in the routing table 

E. They direct traffic from the internet into corporate networks. 

Answer: B,D 

Explanation: 

Cisco administration 101: What you need to know about default routes Reference: 

http://www.techrepublic.com/article/cisco-administration-101-what-you-need-to-know-about-default-routes/ 


Q55. - (Topic 7) 

When enabled, which feature prevents routing protocols from sending hello messages on an interface'? 

A. virtual links 

B. passive-interface 

C. directed neighbors 

D. OSPF areas 

Answer:

Explanation: You can use the passive-interface command in order to control the advertisement of routing information. The command enables the suppression of routing updates over some interfaces while it allows updates to be exchanged normally over other interfaces. With most routing protocols, the passive-interface command restricts outgoing advertisements only. But, when used with Enhanced Interior Gateway Routing Protocol (EIGRP), the effect is slightly different. This document demonstrates that use of the passive-interface command in EIGRP suppresses the exchange of hello packets between two routers, which results in the loss of their neighbor relationship. This stops not only routing updates from being advertised, but it also suppresses incoming routing updates. This document also discusses the configuration required in order to allow the suppression of outgoing routing updates, while it also allows incoming routing updates to be learned normally from the neighbor. 


Q56. - (Topic 1) 

Which two statements describe the operation of the CSMA/CD access method? (Choose two.) 

A. In a CSMA/CD collision domain, multiple stations can successfully transmit data simultaneously. 

B. In a CSMA/CD collision domain, stations must wait until the media is not in use before transmitting. 

C. The use of hubs to enlarge the size of collision domains is one way to improve the operation of the CSMA/CD access method. 

D. After a collision, the station that detected the collision has first priority to resend the lost data. 

E. After a collision, all stations run a random backoff algorithm. When the backoff delay period has expired, all stations have equal priority to transmit data. 

F. After a collision, all stations involved run an identical backoff algorithm and then synchronize with each other prior to transmitting data. 

Answer: B,E 

Explanation: 

Ethernet networking uses Carrier Sense Multiple Access with Collision Detect (CSMA/CD), a protocol that helps devices share the bandwidth evenly without having two devices transmit at the same time on the network medium. CSMA/CD was created to overcome the problem of those collisions that occur when packets are transmitted simultaneously from different nodes. And trust me, good collision management is crucial, because when a node transmits in a CSMA/CD network, all the other nodes on the network receive and examine that transmission. Only bridges and routers can effectively prevent a transmission from propagating throughout the entire network! So, how does the CSMA/CD protocol work? Like this: when a host wants to transmit over the network, it first checks for the presence of a digital signal on the wire. If all is clear (no other host is transmitting), the host will then proceed with its transmission. But it doesn’t stop there. The transmitting host constantly monitors the wire to make sure no other hosts begin transmitting. If the host detects another signal on the wire, it sends out an extended jam signal that causes all nodes on the segment to stop sending data (think, busy signal). The nodes respond to that jam signal by waiting a while before attempting to transmit again. Backoff algorithms determine when the colliding stations can retransmit. If collisions keep occurring after 15 tries, the nodes attempting to transmit will then time out. 


Q57. - (Topic 3) 

What is the OSPF default frequency, in seconds, at which a Cisco router sends hello packets on a multi-access network? 

A. 10 

B. 40 

C. 30 

D. 20 

Answer:

Explanation: 

On broadcast multiacess and point-to-point links, the default is 10 seconds. On NBMA, the default is 30 seconds. 


Q58. DRAG DROP - (Topic 5) 

Drag the appropriate command on the left to the configuration task it accomplishes. (Not all options are used.) 

Answer: 


Q59. - (Topic 5) 

Which two of the following are true regarding the configuration of RouterA? (Choose two.) 

A. At least 5 simultaneous remote connections are possible 

B. Only telnet protocol connections to RouterA are supported C. Remote connections to RouterA using telnet will succeed 

D. Console line connections will nevertime out due to inactivity 

E. Since DHCP is not used on Fa0/1 there is not a need to use the NAT protocol 

Answer: A,C 


Q60. - (Topic 1) 

Refer to the exhibit. 

If host A sends an IP packet to host B, what will the source physical address be in the frame when it reaches host B? 

A. 10.168.10.99 

B. 10.168.11.88 

C. A1:A1:A1:A1:A1:A1 

D. B2:B2:B2:B2:B2:B2 

E. C3:C3:C3:C3:C3:C3 

F. D4:D4:D4:D4:D4:D4 

Answer:

Explanation: 

When packets transfer from one host to another across a routed segment, the source IP address always remains the same source IP address, and the source physical (MAC) address will be the existing router’s interface address. Similarly, the destination IP address always remains the same and the destination physical (MAC) address is the destination router’s interface address.