May 5, 2017 Following our blog on, here is a look at the fundamentals of MPLS VPN and some of the most frequently used MPLS VPN terminology. To start, Multi-Protocol Label Switching (MPLS) is a switching technique where packets are forwarded from a source to destination using labels rather than using hop-by-hop IP based forwarding. The label-based forwarding technique of MPLS is leveraged by network operators, service providers, enterprises, and even data centers to provide services such as VPN (VPLS, Layer 3 VPN, MVPN, etc.), traffic engineering (MPLS-TE, RSVP-TE), and protection (FRR). And now to MPLS VPN fundamentals. MPLS-based Virtual Private Network (VPN) Before MPLS VPN, organizations requiring VPN connectivity used that were expensive and complex. These models also could not isolate customers and had scaling issues when having to manage a large number of tunnels.

But the advent of MPLS made it possible to run VPN services over MPLS, giving it a over the traditional VPN models that were widely in use. MPLS VPN allows for the creation of virtual private networks using MPLS. There are three types of MPLS VPNs that are in use: • Point-to-Point (Pseudowire) • Layer 2 MPLS VPN or VPLS • Layer 3 MPLS VPN Before we look at what each of the VPN types are, let us look at some of the frequently used terminology related to MPLS VPN. MPLS Router Roles The routers that are part of an MPLS network have different roles that are important to understand when describing MPLS VPN services. Let us look what these roles are. P (Provider Router): A core router that is part of the service provider MPLS network and forms a label switched path (LSP). PE (Provider Edge Router): These are devices that sit at the edge of the MPLS network and connect the MPLS network to the customer’s edge routers known as the CE router.

Download android sdk platform tools. A comprehensive introduction to all facets of MPLS theory and practice Helps networking professionals choose the suitable MPLS application and design for their network Provides MPLS theory and relates to basic IOS configuration examples The Fundamentals Series from Cisco Press launches the basis to readers for understanding the purpose.

CE (Customer Edge Router): These devices sit at the edge of the customer network and connect to the MPLS network over the PE device. CE devices are part of a VRF (see below) on the PE device. VRF (Virtual Routing and Forwarding) A technology that allows multiple routing and forwarding tables to exist on a device. This allows a PE router to appear as multiple routers to CE routers.

The PE router maintains a distinct routing table within the specific VRF of each CE router that is connected to it, allowing IP address space to be reused among multiple domains or customers. Route Distinguisher While VRFs allow for the same IP space to be reused by distinct routing domains, it is the route distinguisher (RD) that distinguishes a set of routes that are part of one VRF from another. An RD is a unique number that is added to each route within a VRF, which helps other routers to identify the routes as belonging to that specific VRF or customer. Route Target Route Targets are identifiers added to routes to enable a router to know which routes must be inserted into which VRFs.

A route target allows the router to control the import and export of routes among different VRFs. Other terminologies such as LSP, LER, LSR, and LDP, which we covered in the MPLS Fundamentals blog, also apply to MPLS VPN. And now let’s get back to the different types of MPLS VPNs. Point-to-Point (Pseudowire) Pseudowire is a term used to describe an emulated layer 2 point-to-point connection delivered over MPLS using LDP as its signaling mechanism.

Pseudowire is also referred to as AToM (Any Transport over MPLS) by Cisco. This VPN service uses virtual leased lines (VLL) to provide layer 2 point-to-point connectivity between two sites to carry Ethernet, frame relay or ATM data, and can even interconnect two different types of media – say, Ethernet and Frame Relay.