MPLS routing and control structure

The CCIP exam 642-611-Implementing Cisco MPLS exam course tests these skills.

You must understand that there are multiple concepts related to the entire MPLS structure. The MPLS structure defines how the IP backbone network establishes a tag forwarding table and the communication service that actually provides the forwarding label. The key concepts are as follows: Forwarding Equivalence Class, MPLS control panel, MPLS Forwarding panel, and label distribution protocol.

MPLS routers basically forward tag packets in the same way as IP packets. The MPLS Router will check the labels on the packets that enter the network, and then consult the forwarding table to verify the interface for forwarding the label packets. Next, it will forward the packets.

The key to completing this process is that the router must establish such a label forwarding table. The routing protocol uses dynamic routing protocols such as OSPF and BGP to exchange information between routers. Creating a tag forwarding table requires many steps. The MPLS control panel is responsible for binding a label to the network router in the IP route table and forwarding the binding results to other MPLS routers. The MPLS Control Panel uses the label forwarding protocol to exchange labels between MPLS routers. An MPLS Router is assigned a local label and an exit label that broadcasts messages to neighbors.

MPLS uses the concept of Forwarding Equivalence Class (FEC) to specify a group of IP packets bound with specific tags. An IP data packet group is a loose condition, which actually refers to an IP prefix or a route. FEC can also be smaller and only serve as a network prefix, because it can also specify a specific IP prefix together with other rules such as the ip tos field.

Therefore, the router can find the FEC from the IP routing table and assign it a label. Then, the router sends a notification to other vrouters with tags assigned to FEC. The FEC list with tags assigned is called LIB (list information library ). The router makes forwarding decisions based on information in LIB. Tags actually used for forwarding should be placed in the tag forwarding information library (LFIB. This is the MPLS Forwarding plane.

Now let's sum up. The MPLS Control Panel assigns tags to IP Routers/prefixes in the IP route table. Create a label forwarding table on the MPLS Forwarding panel. This tag forwarding table indicates the interface from which the tags will be forwarded and the tag information that will be exchanged during tag distribution.

The next step for the router to complete is to establish a label exchange path through the network. This is a virtual path where traffic is forwarded from one end of the network to the other.

In terms of Label Distribution and label forwarding, this is the main premise of MPLS label exchange. Be sure to thoroughly understand these concepts. Article entry: csh responsible editor: csh