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Scenario Answers 381

Number scheme solution:

From Router 1, the local DLCIs are 104, 102, and 103. Let's look at an example:

Interface serial0.104
Description to Router 4
Frame Relay Interface DLCI 104
Interface serial0.102
Description to Router 2
Frame Relay Interface DLCI 102

Interface serial0.103
Description to Router 3
Frame Relay Interface DLCI 103

The significance of the 1 is that you start with Router 1. The significance of the 0 is that
the Frame Relay network (represented by the cloud) is the 0. The 4 represents the router
that the DLCI is going to. You simply repeat this from router to router.

Let's look at Router 4:

Interface serial0.401
Description to Router 1
Frame Relay Interface DLCI 401
Interface serial0.402
Description to Router 2
Frame Relay Interface DLCI 402

Interface serial0.403
Description to Router 3
Frame Relay Interface DLCI 403

As you can see, the provider has connected these DLCIs in the provider network with the
Frame Relay switches. For example, DLCI 104 is connected to 401 in the Frame Relay
network. See Figure 10-29.

This is not the only way this scheme could be accomplished. If you figured out a solution
to this scenario, you are on your way to understanding and designing Frame Relay.

Answer to Scenario 3

There are other ways of meeting the company's requirements. This is only a
recommended solution that meets the requirements placed on the CCDP.

Figure 10-30 depicts a recommended solution. There are four remote sites. Each router
has a connection to two different service providers. This is common in redundant Frame
Relay networks and is called a hierarchical mesh. Let's take a look at what happens from
Router A's standpoint. If Router A loses a serial link from S0, all traffic will be directed
over S1 through Service Provider B. The same thing would happen with Routers B, C, and
D. If a problem developed in one of the service provider networks and the whole Frame

87200333.book Page 381 Wednesday, August 22, 2001 2:53 PM