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Seamless MPLS Support in Junos Space Overview

MPLS-based Layer 2 services are growing in demand among enterprise and service providers, creating new challenges related to interoperability between Layer 2 and Layer 3 services for service providers who want to provide end-to-end value-added services. Service providers are able to expand service offerings, support multiple Layer 2 services and protocols at the same time, and to expand geographically by stitching different Layer 2 services to one another and to Layer 3 services, moving toward a seamless MPLS environment..

Interconnecting a Layer 2 VPLS network with a Layer 3 network enables the sharing of a service provider's core network infrastructure between IP and Layer 2 services, reducing the cost of providing those services. A Layer 2 MPLS circuit allows service providers to create a Layer 2 circuit service over an existing IP and MPLS backbone.

Service providers do not have to invest in separate Layer 2 equipment to provide Layer 2 services. A service provider can configure a provider edge router to run any Layer 3 protocol in addition to the Layer 2 protocols. Customers who prefer to maintain control over most of the administration of their own networks want Layer 2 circuit connections with their service provider instead of a Layer 3 VPN connection.

Using MPLS pseudowires makes it possible to encapsulate Layer 2 packets and extend Layer 2 services into Layer 3 networks. Junos Space supports the trend toward accomplishing Seamless MPLS with these two features:

  • VPLS Access Into Layer 3 Networks

  • Pseudowire Access Into a Layer 3 VPN

VPLS Access Into Layer 3 Networks

Integrated Routing and Bridging (IRB) provides simultaneous support for Layer 2 bridging and Layer 3 routing within the same bridge domain, and as well as in the same routing instance. If the IRB interface configured as a Layer 3 interface is being used in a routing instance, that routing instance will specifically declare it as routing-interface rather than regular VPLS interface (which acts like the interface on a specific VPLS Site). This feature requires a normalized VLAN (vlan-id=xxx which is the same as the unit name on which the inet4 address is specified)

VPLS network topology connecting Sites A to D via Provider Edge routers PE-0 to PE-3 with a Layer 3 network linked through PE-3.

Junos Space uses the two peer subinterfaces of the IRB to create the link between an existing VLAN and the Layer 3 network. An extra VPLS node is required to support the IRB interface which allows the rest of the VPLS nodes to be able to access all Layer 3 networks reachable through that interface. Providing the VPLS access into Layer 3 networks enhances basic VPLS services. Because this feature requires a normalized VLAN, it is available only on the Juniper Networks MX 3D Router series.

Pseudowire Access Into Layer 3 VPNs

While technically not a VPLS feature, Junos Space uses pseudowires, also known as pseudowire stitching, to link Layer 2 services together and to Layer 3 services. Pseudowire access into the L3 VPN enhances the standard E-Line LDP and E-Line services. The link into the L3VPN network can be port-based or VLAN-based. At least one node in the peer must be a logical tunnel (LT) interface. The peer must appear in the L3VPN configuration.

Network diagram of L3VPN architecture with PE routers labeled PE-0, PE-1, and PE-2 using BGP, UNI interfaces, and pseudowire connection.

In Junos, this Layer 2 access into Layer 3 VPNs is accomplished by using a tunnel PIC to create a peer link between pseudowire and a Layer 3 network interface.

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