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Look at Assigment in file. The book can also be found there. Read chapter 5 and answer the question. Please include Page numbers for each question.

Homework 5

Submit this assignment via the assignment link on Blackboard in PDF format. Assignment submissions in any other means (email, etc) will not be graded and you will receive a 0. If you submit a word file, you will be docked 10 points. This requirement is to protect both of us.

1. (4 pts) What is the difference between centralized and decentralized routing algorithms? Give an example of each.

 

2. (3 pts) What is the primary reason to use a dynamic routing protocol?

 

3. (3 pts) What is the primary reason to use static routing?

 

4. (2 pts) Using the topology show in P3 on page 429 of your text, what is the least-cost path from router T to router Z? Your answer should be in the form of A->B->C->D and you should list the total path cost.

 

5. (15 pts) Refer to the topology shown in P3 on page 429 of your text. With the indicated link costs, use Dijkstra’s shortest-path algorithm to compute the shortest path from router u to all network nodes. Show each step of the algorithm by computing a table similar to Table 5.1.

 

6. (6 pts) List the strengths of Link-State routing protocols over Distance-Vector routing protocols.

 

7. (2 pts) As a network administrator, why would you ever choose to use a Distance-Vector routing protocol?

 

8. (12 pts) A forwarding table is constructed from routing tables maintained by two different routing protocols.  The lower administrative distance is considered to provide better routing information. Consider the routing tables for the IS-IS protocol and the OSPF routing protocol on a router in the network.  Use the information in the two routing tables to fill in the forwarding table below the two routing tables.

IS-IS Routing Table (Admin Distance 115)
Network	Distance	Next hop
122.38.41.0/24	0	attached
122.38.42.0/25	3	122.38.41.3
122.38.43.0/25	2	122.38.41.3
116.16.0.0/16	3	attached

OSPF Routing Table (Admin Distance 110)
Network	Distance	Next hop
122.38.42.0/24	7	122.38.41.6
122.38.42.0/25	5	122.38.41.19
116.16.0.0/16	0	attached
116.16.87.0/25	1	116.16.1.1

 

 

 

 

Forwarding Table
Network	Source Protocol	Next Hop
0.0.0.0/0	Static	32.14.1.9

 

 

 

 

 

 

 

 

 

 

 

 

9. (4 pts) Using the forwarding table you constructed in the previous question, what is the next hop of each of the following packets with the given destination addresses?
   122. 38.42.131
   123. 16.12.9
   124. 39.201.142
   125. 38.43.93

 

10. (2 pts) What are two commonly-used intra-AS routing protocols?

 

11. (4 pts) Describe the benefits of using OSPF as the intra-AS routing protocol in a network.

 

12. (4 pts) What is meant by an area in an OSPF autonomous system? Why was the concept of an area introduced?

 

13. (2 pts) What type of routing algorithm is used by OSPF?

 

14. (2 pts) Do all routers that need to communicate with each other have to use the same intra-AS routing protocol? What about inter-AS?

 

15. (2 pts) What is the purpose of the BGP routing protocol?

 

16. (2 pts) What is the difference between a gateway router and an internal router for the sake of BGP?

 

17. (8 pts) Explain how BGP determines the best route to a given destination prefix.

 

18. (2 pts) What type of routing algorithm is used by BGP?

 

19. (6 pts) Refer to the figure in P14 on page 431 of your text. Suppose AS3 and AS2 are running IS-IS for their intra-AS routing protocol. Suppose AS1 and AS4 are running OSPF for their intra-AS routing protocol. Suppose eBGP and iBGP are used as the routing protocol for all inter-AS routing. There is no link between AS2 and AS4.
    1. Router 3c learns about prefix x from which routing protocol: OSPF, IS-IS, eBGP, iBGP?
    2. Router 3a learns about prefix x from which routing protocol?
    3. Router 4c learns about prefix x from which routing protocol?
    4. Router 4a learns about prefix x from which routing protocol?
    5. Router 2a learns about prefix x from which routing protocol?
    6. Router 2c learns about prefix x from which routing protocol?

 

20. (2 pts) What is the most common use for ICMP?

 

21. (2 pts) What is the most widely used ICMP error message?

 

22. (6 pts) Explain the mechanism by which traceroute is able to find and display the path from a source to a destination.

 

23. (5 pts) Refer to the topology shown in P3 on page 429 of your text. Assume that a Distance-Vector routing protocol is used on the network and has fully converged (all routers know the shortest path to each destination). Give the output of a simulated traceroute from a host connected to router u to a host connected to router z.