Three-Part Scenarios | Kickoff

Three-Part Scenarios

15 Mar

Three-Part Scenarios
This section contains three three-part scenarios that require planning, configuration, and verification. The solutions to these three-part scenarios are contained within each scenario.

Scenario 19-4
Part A of Scenario 19-4 begins with some planning guidelines that include planning IP addresses, designing the VLSM addressing scheme, identifying the OSPF areas, and determining what type of areas they should be. After you complete Part A, Part B of the scenario asks you to configure the three routers to implement the planned design and a few other features. Finally, Part C asks you to examine router command output to discover details about the current operation. Part C also lists some questions related to the user interface and protocol specifications.

Scenario 19-4, Part A—Planning
Your job is to deploy a new network with three sites, as shown in Figure 19-6.

The OSPF network has a shortage of IP addresses. It has been decided to readdress the network using VLSM. For Part A of this scenario, perform the following tasks:

1. Plan the IP addressing, using the Class B address of 131.99.0.0. Each site consists of two buildings, with seven floors. Each floor has approximately 100 devices. The company plans to install an ISDN backup link between the buildings.

2. In the expectation of growth, the company has decided that each site should be an area. Currently, each site has only two buildings. The floors of each building are connected via a switch. One of the sites has a department running UNIX servers that are using RIP. The RIP networks are redistributed into the OSPF network.

Define the location of the areas.
For each router, define the router type and the number of each area connected. State your reasons for your choices.

Figure 19-6 Scenario 19-4 Network Diagram

Table 19-1 and Table 19-2 are provided to show how to record your IP subnets when performing the planning tasks for this scenario.

Table 19-1 Scenario 19-4, Part A—IP Subnet Network Planning Chart

Table 19-1 Scenario 19-4, Part A—IP Subnet Network Planning Chart (Continued)

Table 19-1 Scenario 19-4, Part A—IP Subnet Network Planning Chart (Continued)

Table 19-1 Scenario 19-4, Part A—IP Subnet Network Planning Chart (Continued)

Solutions to Scenario 19-4, Part A—Planning
Keeping the design as simple as possible—yet not too simple, so that it is still useful as the network evolves—is a good practice. In the suggested answers in Tables 19-3 and 19-4, a numbering scheme is presented. Remember, this is one of many solutions available. The reasoning behind this planning is to allow summarization at the area border routers (ABRs). The first few bits in the third octet indicate the summarization bits. Note that these bits reflect the area; 1 bit, or 128, identifies Area 1, while 3 bits, or 224, identify Area 3.

Table 19-3 Scenario 19-4, Part A—IP Subnet Network Planning Chart Solution

Table 19-3 Scenario 19-4, Part A—IP Subnet Network Planning Chart Solution (Continued)

Table 19-3 Scenario 19-4, Part A—IP Subnet Network Planning Chart Solution (Continued)

Table 19-3 Scenario 19-4, Part A—IP Subnet Network Planning Chart Solution (Continued)

Table 19-4 Part A—OSPF Area Planning Chart Solution

Scenario 19-4, Part B—Configuration
The next step in your job is to deploy the network designed in Scenario 19-4, Part A. Use the solutions for Part A of Scenario 19-4 to direct you in configuring the addressing and summarization at the ABRs. For Scenario 19-4, Part B, perform the following tasks:

1. Configure basic OSPF for Routers A, B, and C based on the design in Scenario 19-4, Part A.
2. Configure summarization on Routers A, B, and C.
3. Configure Routers A and B to connect to stub areas.

Solutions to Scenario 19-4, Part B—Configuration
Example 19-1, Example 19-2, and Example 19-3 show the configurations for Scenario 19-4, Part B, given the criteria.

Example 19-1 Scenario 19-4 Router A Configuration for Questions 1, 2, and 3

Example 19-2 Scenario 19-4 Router B Configuration for Questions 1, 2, and 3

Scenario 19-4, Part C—Verification and Questions
Answer the questions following Example 19-4. Use Example 19-4 as a reference when the question refers directly to this scenario. Although not all of these questions are directly tied to Part A of this scenario, they all probe foundational knowledge required by the technology examined in this scenario.

NOTE In the network from which these commands were captured, several administrative settings not mentioned in the scenario were configured. For instance, the enable password was configured. Any show running-config commands in the examples in this chapter might have other unrelated configuration.

Example 19-4 The show and debug Output Screens for Scenario 19-4, Router A

Example 19-4 The show and debug Output Screens for Scenario 19-4, Router A (Continued)

Answer the following questions:

1. Which command do you use to configure a totally stubby area?
2. What do the letters ASBR stand for, and what does this device do?
3. Where is summarization performed in OSPF?
4. Give the command to configure the ASBR to summarize the networks 131.99.224.128, 131.99.224.224, and 131.99.224.0 through 131.99.230.0 for redistribution into the RIP process, using a 20-bit subnet mask.
5. Explain the difference between prefix routing and subnetting.
6. State one consideration when configuring multiarea OSPF across a nonbroadcast multiaccess (NBMA) network.
7. What command do you use to turn on OSPF?
8. Explain why OSPF supports VLSM.
9. Explain why all areas must connect through the backbone Area 0.
10. Explain the purpose of the network command in OSPF.
11. Which command do you use to show a router’s internal OSPF routing table?
12. Which command shows the use of VLSM on the OSPF network?
13. Which command verifies the establishment of adjacencies with other routers on the same network?
14. How would you determine whether there is more than one IP routing protocol running on a router? If more than one IP routing protocol is running, how would you know how redistribution was configured?
15. When troubleshooting an OSPF configuration over an NBMA network, which command shows the network type that has been configured? The command show running will display this information, but greater analysis of the timers and costs is required.
16. Give the appropriate mask to use on a point-to-point serial interface, where IP unnumbered is not an option.
17. What command would you use to identify that an adjacency could not be formed because one router was configured as a stub, while another was not?
18. Which command do you use to ensure that the virtual link is active?
19. What concern should you have when using the debug command?
20. What is a floating static route, and when would you use one?

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