Understanding MPLS: Basic MPLS Configuration May 2

Filed under Ip Communications, Technology, notquiteleet by leet | 3 comments

Basic Configuration of an MPLS network

The configuration of a basic MPLS network is actually very simple and only requires a few basic steps. The requirements of such a network are the following:

1. Enable CEF: CEF is essentially what allows the imposition and disposition of labels in an MPLS network. You must make sure it is enabled globally, as well as on the specific interfaces participating in the MPLS network. How to enable CEF globally and on interfaces will be shown later. When possible enable CEF in distributed mode, which is largely platform dependent. Unfortunately it does not to pertain to the platforms used in this lab.

2. Configure IGP routing protocol: Interior Gateway Protocols are routing protocols such as RIP, IGRP, EIGRP, and OSPF. In this case OSPF was used on all the routers. The configuration of this relevant to the lab will be shown later. IGP routing protocols are needed to populate the routing tables, which CEF operation takes over and label binding ensues.

(more…)

Understanding MPLS: MPLS in Layered Communciations May 2

Filed under Ip Communications, Technology, notquiteleet by leet | 2 comments

What is its MPLS’ place in layered communication?

It is a niche all its own with no other competitors, MPLS has a complete monopoly in layered communications. Often referred to as switching at layer 2.5, MPLS uses a shim header that contains information that helps move frames from hop to hop.

A shim header is a 32 bit header placed between the layer 2 header, and layer 3 payload as shown in the picture below. In certain applications like MPLS VPN and MPLS TE, the shim header can contain enough information to define a path through an entire network, not just to the next hop. The standard shim header has 4 fields, of which the functions are defined below.

The 4 fields are:

(more…)