Cisco CCNA mock exam questions sample test – Question 126

.In the diagram below, when a packet sent from the PC at 10.0.1.3 to the PC at 10.1.1.3 leaves the Fa0/1 interface of R1, what will be the source and destination IP and MAC
addresses?

A. source IP 10.1.1.2 destination IP 10.1.1.3
Source MAC ad.ad.ad.ad.ad.ad destination MAC ab.ab.ab.ab.ab.ab
B. source IP 10.1.1.1 destination IP 10.1.1.3
Source MAC ad.dd.dd.dd.dd.dd.dd destination MAC ab.ab.ab.ab.ab.ab
C. source IP 10.0.1.3 destination IP 10.1.1.3
Source MAC ad.ad.ad.ad.ad.ad destination MAC ae.ae.ae.ae.ae.ae
D. source IP 10.0.6.3 destination IP 10.1.1.3
Source MAC ad.ad.ad.ad.ad.ad destination MAC ae.ae.ae.ae.ae.ae

Correct Answer: C

Explanation:
The source IP address will be 10.0.1.3 and the destination IP address will be 10.1.1.3. The source MAC address will be ad.ad.ad.ad.ad.ad and the destination MAC address will be
ae.ae.ae.ae.ae.ae.
The source and destination IP addresses never change as the packet is routed across the network. The MAC address will change each time a router sends the packet to the next
router or to the ultimate destination. The switches do not change either set of addresses in the header; they just switch the frame to the correct switch port according to the MAC
address table. Therefore, when the packet leaves R1, the source MAC address will be that of R1 and the destination MAC address will be that of the Fa0/0 interface of R2. The IP
addresses will be those of the two workstations, 10.0.1.3 and 10.1.1.3.
When the workstation at 10.0.1.3 starts the process, it will first determine that the destination address is in another subnet and will send to its default gateway (10.0.1.2). It will perform
an ARP broadcast for the MAC address that goes with 10.0.1.2, and R1 will respond with its MAC address, bb.bb.bb.bb.bb.bb.
After R2 determines the next-hop address to send to 10.0.1.3 by parsing the routing table, it will send the packet to R1 at 10.0.6.2. When R2 receives the packet, R2 will determine
that the network 10.0.1.0/24 is directly connected and will perform an ARP broadcast for the MAC address that goes with 10.0.1.3. The workstation at 10.0.1.3 will respond with its
MAC address, ab.ab.ab.ab.ab.ab.
Objective:
Routing Fundamentals
Sub-Objective:
Describe the routing concepts
References:
Cisco > IOS Technology Handbook > Routing Basics