Scenario Answers


The answers provided in this section are not necessarily the only possible answers to the questions. The questions are designed to test your knowledge and to give practical exercise in certain key areas. This section is intended to test and exercise skills and concepts detailed in the body of this chapter.

If your answer is different, ask yourself whether it follows the tenets explained in the answers provided. Your answer is correct not if it matches the solution provided in the book but rather if it has included the principles of design laid out in the chapter.

In this way, the testing provided in these scenarios is deeper: It examines not only your knowledge but also your understanding and capability to apply that knowledge to problems.

If you do not get the correct answer, refer back to the text and review the subject tested . Be certain to also review your notes on the question to ensure that you understand the principles of the subject.

Scenario 5-1 Answers


Using appropriate addressing and in reference to Figure 5-1, state where the routers should be placed.


The routers should be placed in each location, with the option of adding routers within each building if the network grows considerably.


The administrator has decided that a link-state routing protocol is the best solution for this network design. Justify this choice, explaining which characteristics of the link-state routing protocol would benefit this network.


A link-state routing protocol would be a good choice because of the large number of WAN interfaces. A distance vector routing protocol would increase congestion across these low-bandwidth links. The capability to use VLSM and to summarize these points would be an added advantage.


The administrator must create an implementation plan for the team. List the IP routing protocol requirements for every router that might be used as a checklist for the installation staff.


Each person implementing the routing protocol on the router would have to ensure the following:

- The appropriate interfaces have IP addresses that are on the same subnet as the other devices on the segment.

- The routing protocol is configured correctly with the correct network addresses.

- The routing table reflects the logical topology map of the network and all the remote networks are present.

- If there are multiple paths available of equal cost, the routing protocol should be load sharing between the paths. This means all the paths are present in the routing table.


The links between the various sites are leased lines with a backup link using a dialup line. Should the administrator be aware of any considerations?


The leased lines to the remote sites could be configured to be the primary link; as such, no traffic would traverse the dialup links. However, routing updates would be propagated out of the dialup links so that the routing table would be aware of the potential path. To prevent this (and, thus, the dialup line being raised), the path could be manually entered into the routing table. However, this would render it the preferred path . Configuring the dialup paths as floating static routes would ensure that they were used only if the primary line failed, without having to generate network traffic across the link to maintain the routing table.

Table 5-6 summarizes the major differences between distance vector routing protocols and link-state routing protocols.

Table 5-6. Distance Vector Routing Protocols Versus Link-State Routing Protocols

Distance Vector


Sends its entire routing table (typically every 30 seconds).

Sends incremental updates. It synchronizes the routing tables every 15 or 30 minutes.

Updates sent using a broadcast.

Uses a multicast address for updates.

Uses a metric based on how distant the remote network is to the router.

Is capable of using a complex metric.

Routing information learned from its neighbors.

Routing information learned from every router in the area.

The routing table is viewed from the perspective of each router.

The topological database is the same for every router in the area.

Uses Bellman Ford algorithm.

Uses the Dijkstra algorithm.

Does not consume many router resources, but is heavy in the use of network resources.

Uses many router resources, but is relatively low in its demand for network resources.

Maintains one domain in which all the routes are known.

Has a hierarchical design of areas that allow for summarization and growth.

Restricted by classful addressing scheme.

For effective use, the addressing scheme should reflect the hierarchical design of the network.

Involves slower convergence.

Involves quicker convergence.

CCNP BSCI Exam Certification Guide
CCNP BSCI Exam Certification Guide (CCNP Self-Study, 642-801) (3rd Edition)
ISBN: 1587200856
EAN: 2147483647
Year: 2002
Pages: 194
Authors: Clare Gough © 2008-2017.
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