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6. Which row is the best-match row for the following packets? 172.29.8.45 172.30

ID: 3606168 • Letter: 6

Question

6. Which row is the best-match row for the following packets?

172.29.8.45

172.30.33.62

60.168.5.43

172.0.12.76

213.128.96.78

47

7. The following rows match:

Row 234         Prefix /12        Metric 100 (higher is better)

Row 78          Prefix /19        Metric 50

Which is the best-match row?

8. The following rows match:

Row 163                    Prefix /9           Metric 30 (lower is better)

Row 543         Prefix /22        Cost Metric 87

Row 13          Prefix /22        Cost Metric 157

Which is the best-match row?

9. Your IP address is 192.168.1.143

subnet mask is 255.255.255.0

What is subnet address?

Broadcast address?

Number of host on this network?

Host address range?

10. Your IP address is 143.76.1.186

subnet mask is 255.255.0.0

What is subnet address?

Broadcast address?

Number of host on this network?

Host address range?

Row Destination Netowork or Subnet Mask/(Prefix) Metric(Cost) Interface Next-Hop Router 1 128.171.0.0 255.255.0.0 (/16)

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2 G 2 172.30.33.0 255.255.255.0 (/24) 0 1 Local 3 60.168.6.0 255.255.255.0 (/24) 12 2 G 4 123.0.0.0 255.0.0.0 (/8) 33 2 G 5 172.29.8.0 255.255.255.0 (/24) 34 1 F 6 172.40.6.0 255.255.255.0 (/24) 47 3 H 7 128.171.17.0 255.255.255.0 (/24) 55 3 H 8 172.29.8.0 255.255.255.0 (/24) 20 3 H 9 172.12.6.0 255.255.255.0 (/24) 23 1 F 10 172.30.12.0 255.255.255.0 (/24) 9 2 G 11 172.30.12.0 255.255.255.0 (/24) 3 3 H 12 60.168.0.0 255.255.0.0 (/16) 16 2 G 13 0.0.0.0 0.0.0.0 (/0) 5 3 H

Explanation / Answer

6.
    This we will decide by performing AND operation between IP address and Mask.

       1) If there is more than 1 match then consider the one which

          has highest mask length or prefix.

       2) If there is more than 1 match and even if they are having

          same prefix, prefer based on cost(select least cost one).

172.29.8.45

This can belongs to row 5 or row 8. Both are having

same prefix but row 8 metric is < row 5 and

Hence the best Match is row 8.

172.30.33.62

Here we got only 1 row matched and it is row 2.

Hence the best Match is row 2.

60.168.5.43

   Here we got only 1 row matched and it is row 12.

   Hence the best Match is row 12.

172.0.12.76

    Here no row will be matched and hence it will be

    routed in the default route row 13.

213.128.96.78

    Here no row will be matched and hence it will be

     routed in the default route row 13.

7.

     Here row 78 has longest prefix and hence the best match is row 78.

     Even if row 234 has best metric the 1st preference will be to go to prefix.

8.

      Here row 543 and 13 has longest prefix but row 543 has best metric

       and hence the best match is row 543.

9.

     Given IP address is 192.168.1.143 and subnet mask is 255.255.255.0

      Here Number of 1's in mask is 24 hence

      Number of bits in Network id = 24 and Number of bits in Host id = 8

      Subnet address is 192.168.1.143 AND 255.255.255.0 = 192.168.1.0

      Broadcast address is 192.168.1.11111111 = 192.168.1.255

      Number of host on this network is = 28 - 2 = 254

      Host Address Range is 192.168.1.1 to 192.168.1.254

10.

     Given IP address is 143.76.1.186 and subnet mask is 255.255.0.0

      Here Number of 1's in mask is 16 hence

      Number of bits in Network id = 16 and Number of bits in Host id = 16

      Subnet address is 143.76.1.186 AND 255.255.0.0 = 143.76.0.0

      Broadcast address is 143.76.11111111.11111111 = 143.76.255.255

      Number of host on this network is = 216 - 2 = 65534

      Host Address Range is 143.76.0.1 to 143.76.255.254