[Networking – LAB] Basic MPLS topology

While reviewing MPLS topics you can’t avoid to try how the technology works doing some labs. This is particularly valid if you don’t have the opportunity to “touch” the technology with your daily job. That’s why I decided to rebuild the topology of MPLS cloud used in the INE course for the MPLS exam. As always I built it to be used in GNS3 with IOU support and then decided to share it with you.

At the moment the LAB has only the very basic configuration to make easy a review of the MPLS commands and pre-requisites. The next step (that will be covered in one of my future articles) will be to complete the configuration at least to have a complete MPLS VPN infrastructure.

So, after you download the lab from here, you can just answer to the following questions and configure the devices as needed.

First of all let’s have a look at the topology:

MPLS Network Topology (click to enlarge)

At the moment only IPs of all devices are configured. The goal of this lab is to configure a very basic MPLS into the cloud and think about commands to use.

• Answer to some questions

The main step to start is to answer to the following questions:

1. What features are needed to be active on routers for the MPLS to work?
2. Do you need routing protocols within the cloud to make the MPLS working? If so, what kind of routing protocol you need?
3. What is the real difference if you use one routing protocol or another?

After you answer to the above questions you can jump on the devices and start the configuration.

• Configure MPLS in the Cloud

1. First of all check that all the needed “features” are active (check in particular CEF).
2. Configure the chosen routing protocol in the cloud.
3. Configure MPLS: what commands will you need and on what devices ?

• Check if the MPLS is working

1. check on each router if you can see LDP neighbors and eventually tshoot.
2. What commands you can use to check what labels are used to forward packets?
3. What “imp null” label is?
4. check if the packets are indeed forwarded using the labels.

What we did till now is a very basic configuration of the MPLS and I think it can be useful if you want to quickly review it. Next step will be to configure a VPN using MPLS. This will be really exciting and will increase the difficulty of the understanding of MPLS as well as the configuration part. But keep in mind that MPLS is currently used a lot exactly to build VPNs.

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