Ccna certification Practice Tests

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Appendix 

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  Answers to Practice Test Questions

 138.  B.  Using router on a stick (ROAS) is a cheaper alternative to IVR if the current switch does 

not support layer 3 routing. Using ROAS is highly inefficient because all traffic that is routed 

to the router must be routed back, diminishing the bandwidth of the link by 50 percent. 

ROAS can be used with ISL or 802.1Q. ROAS is not limited to a maximum of 16 routes.

 139.  B.  When configuring ROAS on a router’s interface, you should always issue the 

no 

ip address command. No IPs can be configured on the main interface. All IPs are 

configured on the subinterfaces. The command 

ip routing is incorrect. The command ip 

encapsulation dot1q is incorrect. The command sdm routing is incorrect.

 140.  C.  Verifying the proper operation of the switch would start with verifying that the port 

is correctly set as a trunk to the router. If it is not set as a trunk, it would not be able to 

tag frames for the router to direct to the proper interfaces. The command 

show ip route 

is incorrect. The command 

show interface status is incorrect. The command show 

switchport is incorrect.

 141.  C.  When you’re configuring a router interface to accept VLAN tagging, the subinterface 

numbering does not matter. It is recommended that the subinterface match the VLAN 

for readability. However, 

encapsulation dot1q 10 is the command that allows the 

subinterface to accept the frames for VLAN 10. The command 

encapsulation vlan 10 

dot1q is incorrect. The command interface Fa 0/0.10 is incorrect. The command ip 

address 192.168.10.1 255.255.255.0 is incorrect.

 142.  A.  When ROAS is implemented, only the physical interface has a unique MAC address. 

All ARP requests for the IP addresses configured on the subinterfaces respond with the 

same MAC address. They are not unique MAC addresses, but on each VLAN they are 

unique in the sense that no other machines on the VLAN share the same MAC address.

 143.  A.  Each IP address on a subinterface is the routed gateway for the VLAN on that 

subinterface. The main interface should be configured with the 

no ip address command 

when ROAS is configured. The default native VLAN of 1 is configured on the switch side 

only unless you explicitly configure a native VLAN on the router.

 144.  C.  Default routing is a form of static routing. It is used on the edge of a network to direct 

all traffic to the inner core of the network. OSPF routing is a dynamic routing protocol. 

EIGRP is a dynamic routing protocol. RIP is a dynamic routing protocol.

 145.  B.  Static routing is extremely secure because it does not need to broadcast or multicast 

routing updates. These updates can be intercepted or injected into a network to create 

problems. Static routing requires a higher degree of administrative overhead because all 

possible routes must be configured and maintained manually. All routing protocols have 

the potential to create resiliency on a network. Static routing is not scalable because it is 

all manually entered.

 146.  D.  Static routing has the lowest bandwidth overhead because there is no bandwidth 

required to maintain static routes. RIP routing has the highest bandwidth overhead 

because it uses either broadcasts or multicasts to transmit the entire routing table. OSPF 

and EIGRP routing both have higher bandwidth overhead than static routing.

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Chapter 3: IP Connectivity (Domain 3)