Ccna certification Practice Tests

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 41.  C.  The destination MAC address is changed to the router’s MAC address and the 

destination IP address is untouched. The destination IP address is not changed throughout 

the routing process. The destination MAC address is only changed to the destination 

host’s MAC address if the traffic is deemed to be local. The source IP address is not 

changed throughout the routing process unless NAT is being used.

 42.  B.  The TTL, or time to live, is decremented usually by one. When the TTL reaches zero, 

a packet is considered unroutable. This prevents packets from eternally routing. The 

destination IP address is not changed throughout the normal routing process. The source 

MAC address in not changed, since the originator of the frame has no need to forge the 

frame.

 43.  B.  When a packet is determined to be local to the sending host, ARP is used to resolve 

the MAC address for the IP address of the destination host, and the frame is sent directly 

to the host. The destination IP address is not changed throughout the network delivery 

process. The destination MAC address is only changed to the MAC address of the router 

if the packet is deemed to be remote from the immediate network. The source IP address 

is not changed throughout the routing process unless NAT is being used, and NAT is not 

used for local communications.

 44.  B.  The sending host ANDs its subnet mask against the destination IP address, then 

against its IP address, and this give a frame of reference for where it needs to go and where 

it is. The host compares the remote IP to its internal routing table after the calculation 

of local versus remote is performed and the host is ready to route the packet. The host 

does not perform the ANDing process against the destination IP address and destination 

subnet mask because the destination subnet mask is often unknown and irrelevant to the 

calculation. ICMP is not used in the calculation of local versus remote networks.

 45.  D.  The current method of packet forwarding used by Cisco routers is Cisco Express 

Forwarding (CEF). CEF creates several cache tables used for determining the best route 

for the destination network. Process switching is the original method used with routing 

packets and is no longer used. Fast switching is also an older method used with routing 

packets on Cisco devices, and it too is no longer used. Intelligent packet forwarding is not 

a packet forwarding method, and therefore, it is an invalid answer.

 46.  B.  The layer 2 process is called frame rewrite. When a packet hops from router to router, 

the destination frame is rewritten for the next destination MAC address. IP routing is the 

process the router actually performs for the selection of a route or path to the destination. 

Packet hopping is not a valid process in the routing of packets, and therefore, it is an 

invalid answer. Packet switching is the concept of moving packets of data over a digital 

network, and therefore, it is an incorrect answer.

 47.  C.  When a MAC address is unknown for the destination IP address or the default 

gateway, the ARP request is sent in the form of a broadcast. If the destination MAC 

address was the router’s MAC address, the router would be the only device to receive the 

ARP request frame. The host’s MAC address is what we need to process the framing of 

data; therefore, it is the reason for the ARP request to all listening nodes. In IPv4, ARP 

uses broadcasts to forward the ARP request to all listening network devices. Multicast is 

used in IPv6 for node discovery, but it does not use ARP.

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