Practical Applications

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Now that you have seen how data “flows” in an MPLS network, it is time to look at some practical implementations of MPLS and some of the commands that could be useful to you. Of course, different vendors may use different commands, but this section provides some examples.

Label Numbers

The first part of these applications relates to label numbers and how they are used or reserved. The MPLS standard reserves labels 0–15 for defined uses. This leaves labels 16–1,048,575 open for use.

Manufacturers differ on how these labels are assigned. For example, one vendor (Juniper) uses labels 16–1023 for manual LDP connections and configuration, while labels 1024–99,999 are stored for future use. That leaves labels 100,000–1,048,575, which can be assigned by the system automatically.

All manufacturers reserve labels 0–15, but they divide their labels differently. This does not affect interoperability, because labels are negotiated when an LDP is established. If a label is requested, then it cannot be used until another label is assigned.

MPLS Commands

With other routers (such as Cisco), you can assign a label range with a simple command figure, as shown in Figure 1.10.

Figure 1.10: MPLS Label Range Commands

The next useful practical command involves seeing the forwarding tables. Cisco’s example is shown in Figure 1.11.

Figure 1.11: MPLS Forwarding Table Commands

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