EC312 Homework 27

Name: ____SOLUTIONS_______________

1. Given the following ARP table, make the necessary change(s) to cause all Ethernet traffic destined for 192.168.14.10 to flow to you (192.168.14.13) instead?

IP MAC

2. Why is the destination hardware address all 0s in the ARP request message?

Because when a request is made, the sender does not know the destinations hardware address yet. This destination hardware address of all 0s is part of the ARP request packet. It

should not be confused with the datalink layer Ethernet frame which has a destination hardware address of all fs (broadcast address).

3. Why is the destination hardware address of the frame from A to B a broadcast address?

The frame uses a broadcast address so that the intended recipient on the network will receive the frame even though the sender does not know the specific hardware address of the

intended recipient.4. To acquire an IP address, the sourec address is 0.0.0.0 and the destination address is 255.255.255.255.

5. Combine the following three blocks of addresses into a single block:a. 16.27.24.0/26 - 00010000.00011011.00011000.00|000000

Range – 16.27.24.0 to 16.27.24.63 b. 16.27.24.64/26 - 00010000.00011011.00011000.01|000000

Range – 16.27.24.64 to 16.27.24.127 c. 16.27.24.128/25 - 00010000.00011011.00011000.1|0000000

Range – 16.27.24.128 to 16.27.24.255 Total Range - 16.27.24.0 to 16.27.24.255

Combined: 16.27.24.0/24

192.168.14.8 AA:BB:CC:DD:EE:FF192.168.14.9 AA:BB:AA:BB:AA:BB192.168.14.10 A4:B5:C6:D7:E8:F9192.168.14.12 EE:FF: EE:FF:EE:FF192.168.14.13 A4:B5:C6:D7:E8:F9192.168.14.21 C6:D7:C6:D7:C6:D7192.168.14.25 E8:F9: E8:F9:E8:F9

6. Can router R1 in figure below receive a packet with destination address 140.24.7.194? What will happen to the packet if this occurs?

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Figure 22.8 Longest mask matching

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Figure 22.8 Longest mask matching

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Figure 22.8 Longest mask matching

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Figure 22.8 Longest mask matching

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Figure 22.8 Longest mask matching

It can receive a packet with a destination address 140.24.7.194 from Organization 1, 2, or 3. It will route the packet through interface, m3, to router R2.

7. Assume router R2 above has fixed its routing table to have longest mask matching below, and it receives a packet with destination address 140.24.7.42. How is the packet routed to its final destination?

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Figure 22.8 Longest mask matching

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Figure 22.8 Longest mask matching

Router R2 will compare the destination address with its forwarding table. Using the mask, R2 determines if the destination address is part of the 140.24.7.192 network. It is not. R2

compares the destination address with the 140.24.7.0 network. It is part of this network. R2 will forward the packet to R1 via interface m0. When R1 receives the packet, it will use its forwarding table similar to R2, starting at the top and working its way down. In this case, the packet is destined for an IP address that is part of the network 140.24.7.0. R1 will send to packet to the appropriate host in Organization 1 via interface m0.

8. Construct the routing table for router RB in the picture shown below.

Network address/mask Next-hop address Interface2.2.2.4/30 ----- m04.4.4.40/29 ----- m13.3.3.32/27 ----- m20.0.0.0/0 default router (none given in

this problem)