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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)

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 Eline LDP and point-to-point 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.

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.