Ccna certification Practice Tests

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Appendix 

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  Answers to Practice Test Questions

 51.  C.  Time to live (TTL) is a field in the IP header that prevents packets from endlessly 

routing in networks. Each time a packet is routed, the router’s responsibility is to 

decrement the TTL by one. When the TTL reaches zero, the packet is considered 

unrouteable and dropped. The checksum field is used to check for a damaged packet in 

transit. The flags field in the IP packet is to signal if the packet has been fragmented. The 

header length field defines the length of the header of the IP packet.

 52.  A.  Cisco Express Forwarding (CEF) allows the CPU to initially populate a sort of route 

cache called the forwarding information base (FIB). Any packets entering the router can 

be checked against the FIB and routed without the help of the CPU. Process switching 

and fast switching both use the processor directly to make routing decisions. Expedited 

forwarding is not a packet routing technique; it is a quality of service (QoS) method and 

therefore an invalid answer.

 53.  C.  The multicast address of ff02::a is the multicast address for IPv6 EIGRP updates. 

Updates for routers participating in IPv6 EIGRP will be multicast to the IPv6 address of 

ff02::a. Routing Information Protocol Next Generation (RIPng) uses a multicast address 

of ff06::9. Open Shortest Path First version 3 (OSPFv3) uses multicast addresses of ff05::5 

and ff05::6. Stateless Autoconfiguration (SLAAC) uses the link-local address that starts 

with fe80.

 54.  B.  When you see an exclamation mark, it means that the packets were successfully 

acknowledged on the other side and an ICMP response was received. If you see five 

periods returned, it means that the packets have never made it back to the router. 

Congestion in the path will not be visible with the ping command. If the packets are 

received on the far router but ICMP times out, periods will be displayed.

 55.  C.  The extended ping command allows you to specify a number of parameters such 

as repeat count, datagram size, and source address or exit interface. There are several 

other parameters that can be adjusted. You use the extended 

ping command through the 

privileged exec prompt and not the global configuration mode. Configuring a temporary 

route for the router exit interface will affect all traffic on the router.

 56.  C.  The three times are the minimum response time, average response time, and maximum 

response time of the ICMP echo and reply. All other options are incorrect.

 57.  C.  The Ctrl+Shift+6 key sequence will cause a break during a network command such as 

ping or traceroute. The key sequence of Ctrl+C is incorrect. The key sequence of Ctrl+4 

is incorrect. The key sequence of Ctrl+Shift+1 is incorrect.

 58.  B.  When you are diagnosing a network connectivity issue, you always start testing the 

closest IP address. In this case, the default gateway of Router A is the closest IP address. 

The switches are irrelevant because they are not layer 3 devices that can be tested at 

layer 3. The fact that it has an IP address and can return a ping means that you can 

communicate with its management plane. The Internet Control Message Protocol (ICMP) 

packet will traverse the data plane, also called the forwarding plane. All of the other 

options are incorrect.

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Chapter 8: Practice Exam 2