Configuring MPLS L3 VPN on Cisco using GNS3

Configuring MPLS L3 VPN on Cisco using GNS3


2 min read


I have been studying Multi-Protocol Label Switching (MPLS) for a while and I want to show you what I have been learned so far.

Quick Overview

According to Wikipedia's definition of Multi-Protocol Label Switching (MPLS),

"Multiprotocol Label Switching is a routing technique in telecommunications networks that directs data from one node to the next based on labels rather than network addresses. Whereas network addresses identify endpoints, the labels identify established paths between endpoints."

So what does that mean? Multi-Protocol Label Switching (MPLS) is basically an approach in computer networking wherein labels are used to deliver Protocol Data Units (PDUs) instead of the Layer 3 (IP) header. Route lookup on routing devices utilizes the CPU which consumes time before doing the actual forwarding of the packet. This traditional way of delivering traffic can be optimized with Multi-Protocol Label Switching (MPLS).

With the use of Multi-Protocol Label Switching (MPLS) labels, route lookup can be less so routing devices can focus on forwarding rather than performing route lookups.

[NOTE] While today's routers have reliable hardware that can perform IP routing lookup faster, Multi-Protocol Label Switching (MPLS) is still useful for instance, providing a Virtual Private Network (VPN) for Service Provider's customers.

Of course, configuring Multi-Protocol Label Switching (MPLS) in just single router is not useful; It is configured by group, hence, an MPLS network. That's why industry describes it as 'expensive' compared to internet connection plan from your ISP.

Routers insert the Multi-Protocol Label Switching (MPLS) label between the Layer 2 and Layer 3 PDU making it famously called 'Layer 2.5'

[NOTE] Using MPLS labels to forward traffic does not mean IP routing is not used. Layer 3 functionality is still used with the help of an Interior Gateway Protocol (IGP) for the routers in the MPLS network to reach each other creating an underlay for our MPLS label distribution.

I recommend reading some topics regarding protocol. Please see the References section at the bottom of this content to see some useful articles for you to learn some more information about it.


I know it is unsatisfying to be cut here. I do not want you to get tired of scrolling. Quick! have a look in our configuration here.


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