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Configuring MPLS-Signaled LSPs to Use GRE Tunnels

 

MPLS LSPs can use generic routing encapsulation (GRE) tunnels to cross routing areas, autonomous systems, and ISPs. Bridging MPLS LSPs over an intervening IP domain is possible without disrupting the outlying MPLS domain.

LSPs can reach any destination that the GRE tunnels can reach. MPLS applications can be deployed without requiring all transit nodes to support MPLS, or requiring all transit nodes to support the same label distribution protocols (LDP or RSVP). If you use CSPF, you must configure OSPF or IS-IS through the GRE tunnel. Traffic engineering is not supported over GRE tunnels; for example, you cannot reserve bandwidth or set priority or preemption.

Note

Use the no-control word statement to disable the control word when the topology uses GRE as the connection mechanism between provider edge routers and one of the provider edge routers is an M Series Multiservice Edge Router.

For more information about GRE tunnels, see the Junos OS Services Interfaces Library for Routing Devices.

Example: Configuring MPLS-Signaled LSPs to Use GRE Tunnels

To configure MPLS over GRE tunnels:

  1. Enable family mpls under the GRE interface configuration:

  2. Enable RSVP and MPLS over the GRE tunnel:

  3. Configure LSPs to travel through the GRE tunnel endpoint address:

Standard LSP configuration options apply. If the routing table specifies that a particular route will traverse a GRE tunnel, the RSVP packets will traverse the tunnel as well.