Ccna certification Practice Tests

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Appendix 

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  Answers to Practice Test Questions

 48.  A.  Every host contains an ARP cache. This cache allows for lookups of MAC addresses 

for destination IP addresses when the host frequently sends packets to the destination. 

Therefore, there are fewer ARP packets. IP multicasting is used with network discover 

(ND) packets in IPv6 and not ARP. There is no such thing as frame casting; therefore, it is 

an invalid answer. There is also no such thing as an IP cache; therefore, it is also an invalid 

answer.

 49.  B.  After the frame is verified to be addressed to the router and the FCS has been checked, 

the router decapsulates the packet and strips off the frame. The router will only accept 

frames that are unicast directly to the router’s MAC address, multicasted to the router 

multicast group, or broadcast to all devices. Routers must decapsulate packets to inspect 

the destination IP address. Routing decisions are never made by examining the source 

MAC address, since the source of the traffic is irrelevant to the destination.

 50.  D.  The command to display the router’s ARP cache is 

show ip arp. The commands  

show arp, show arp table, and show arp cache are incorrect.

 51.  B.  By default, all entries have a time to live, or TTL, of 240 seconds. They will be 

removed after that period if not used during the 240 seconds. All other answers are 

incorrect.

 52.  D.  Dynamic routing allows for the population of routing tables from advertisements of 

other routers. There are several dynamic routing protocols, such as, for example, EIGRP, 

RIP, and OSPF. Default routing forces all traffic that is unknown to a specific next hop. 

Stub routing is similar to default routing. Stub routing is often used to describe a default 

route on a stub network, where any remote network address is through a specific next 

hop. Static routing is the method of manually configuring route statements in router versus 

dynamic routing protocol processes.

 53.  B.  When a route is found in the routing table, the router will find the gateway for the 

next hop and change the packet’s destination MAC address for the next router. The 

packet’s TTL will always be decremented by one as it passes through a router and is not 

increased. When packets travel through a router, the layer 4 transport information is not 

inspected; only the layer 3 destination IP address is inspected. The packet is never changed 

throughout the routing process, such as adding the destination IP address of the next hop.

 54.  D.  The Internet Control Message Protocol (ICMP) is a layer 3 protocol that allows for 

end-to-end testing with a command such as traceroute. The Internet Group Management 

Protocol (IGMP) is used to allow hosts to join a multicast group on a switch. The RARP is 

used to resolve an IP address from a MAC address; its operation closely resembles DHCP. 

Address Resolution Protocol (ARP) is used to resolve a MAC address from an IP address 

for the purpose of framing data.

 55.  B.  The Routing Information Protocol (RIP) is a distance-vector protocol. Open Shortest 

Path First (OSPF) is a link-state protocol. Enhanced Interior Gateway Routing Protocol 

is a hybrid protocol that more closely resembles a link-state protocol. Border Gateway 

Protocol (BGP) is a path-vector protocol used for Internet routing.

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Chapter 3: IP Connectivity (Domain 3)