The Design Implementation Process

After the design is complete, the design implementation process is executed. Planning a Design Implementation

Planning and documenting the design implementation is the first step in this process. The design implementation description should be as detailed as possible. The more detailed the design documentation, the less knowledgeable the network engineer must be to implement the design. Very complex implementation steps usually require that the designer carry out the implementation, whereas other staff members (or another company) can perform well-documented, detailed implementation steps.

Implementation must consider the possibility of a failure, even after a successful pilot or prototype network test. The plan should therefore include a test at every step and a rollback plan to revert to the original setup if a problem occurs. List implementation steps and estimated times in a table.

If a design is composed of multiple complex implementation steps, plan to implement each step separately rather than all at once. In case of failure, incremental implementation reduces troubleshooting and reduces the time needed to revert to a previous state. Implementation of a network design consists of several phases (install hardware, configure systems, launch into production, and so forth). Each phase consists of several steps, and the documentation for each step should contain the following:

■ Description of the step

■ References to design documents

■ Detailed implementation guidelines

■ Detailed rollback guidelines in case of failure

■ Estimated time necessary for implementation

Figure 2-27 illustrates a sample implementation plan summary.

Figure 2-27 Sample Summary Design Implementation Plan

Date Time

Description

Implementation Details

Complete

Phase 3

04/02/2007

Install campus hardware

Section 6.2.3

Step 1

Connect switches

Section 6.2.3.1

Step 2

Install routers

Section 6.2.3.2

Step 3

Complete cabling

Section 6.2.3.3

Step 4

Verify data link layer

Section 6.2.3.4

Phase 4

04/03/2007

Configure campus hardware

Section 6.2.4

Step 1

Configure VLANs

Step 2

Configure IP addressing

Section 6.2.4.1

Step 3

Configure routing

Section 6.2.4.2

Step 4

Verify connectivity

Section 6.2.4.3

Phase 5

04/02/2007

Launch campus updates into production

Section 6.2.4.4 Section 6.2.5

Step 1

Complete connections to existing network

Section 6.2.5.1

Step 2

Verify connectivity

Section 6.2.5.2

In Figure 2-27, each step of the implementation phase is briefly described, with references to the detailed implementation plan for further details. The detailed implementation plan section should describe precisely what needs to be accomplished.

Figure 2-28 provides a detailed description of an implementation step. It describes the configuration of EIGRP on 50 routers in the network and lists the two major components of the step (in the per-router configuration procedure).

Figure 2-28 Sample Detailed Design Implementation Step

• Section 6.2.7.3, "Configure routing protocols in the WAN network module":

- Number of routers involved is 50.

- Use template from section 4.2.3, "EIGRP details."

- Per router configuration:

• Use passive-interface command on all nonbackbone LANs. (See section 4.2.3, "EIGRP details")

• Use summarization according to the design. (See section 4.2.3, "EIGRP details," and section 4.2.2, "Addressing details")

- Estimated time is 10 minutes per router.

- Roll-back procedure: Remove EIGRP configuration on all routers.

The reference to the design document is useful for retrieving the details about the EIGRP implementation.

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