Module 11

Question 1

List the three next-hop methods for packet forwarding.

Answer 1

Source routing methods using packet header option

• Host specific method
• Network specific method
• Default method

Question 2

List the four most basic fields in routing entries.

Answer 2

Network address, mask, next hop IP, interface

Question 3

Describe the motivations of link state routing and path vector routing.

Answer 3

• Link state uses the quality of the links as a metric

- Path vector uses only hop count

Question 4

Supernet the following addresses.

140.24.7.0, 140.24.7.64, 140.24.7.128, and 140.24.7.192

Answer 4

10001100. 00011000.00000111.00000000 /26
10001101. 00011000.00000111.01000000 /26
10001102. 00011000.00000111.10000000 /26
10001103. 00011000.00000111.11000000 /26

The part that doesn’t change is the supernet

10001100.00011000.00000111.00000000 /24

Question 5

What if a packet is supposed to go to a destination in another AS in a BGP network?

Answer 5

When the destination address is located in a different AS, the packet is forwarded through default routers again and again in the AS to the topmost default gateway which is called the border gateway.

Question 6

In classless addressing we need at least four columns, what are they?

Answer 6

Network address, mask , next hop IP, interface