Vyatta NOS documentation

Learn how to install, configure, and operate Vyatta Network Operating System (Vyatta NOS), which helps to drive our virtual networking and physical platforms portfolio.

Setting up paths

A path is a list of router hops that specifies a route across an MPLS domain.

Once you create a path, you can create signaled LSPs that use the path. Paths are configured separately from LSPs so that a path may be specified once and then used by several LSPs that see the path by name. There can be one primary path and one optional secondary path.

A path is always configured at the ingress LER and assumes that the ingress LER is the beginning of the path. A path can contain any number of nodes, which correspond to MPLS-enabled routers in the network. Each node has one attribute: whether it is strict or loose. A strict node means that the router must be directly connected to the preceding node. A loose node means that there can be other routers in between.

Creating a path is not absolutely necessary when configuring an LSP. When you configure a signaled LSP without naming a path, CSPF uses only information in the Traffic Engineering Database (TED), as well as the user-configured attributes and requirements of the LSP to calculate the path.

  1. Define the explicit route path.
    vyatta@R1# set protocols mpls-rsvp globals explicit-paths sf_to_sj
    In this example the explicit route path is sf to sj.
  2. Configure the loose node.
    vyatta@R1# set protocols mpls-rsvp globals explicit-paths <name> explicit-route-objects <0-255> action loose
    vyatta@R1# set protocols mpls-rsvp globals explicit-paths <name> explicit-route-objects <0-255> address <ip-address>
  3. Configure the strict node.
    vyatta@R1# set protocols mpls-rsvp globals explicit-paths sf_to_sj explicit-route-objects <0-255> action strict
    vyatta@R1# set protocols mpls-rsvp globals explicit-paths sf_to_sj explicit-route-objects <0-255> address <ip-address>

The path is assumed to start from the local node. You specify the nodes in order from ingress to egress. Specifying the local node itself as the first node in the path is optional. Further, the final node does not necessarily have to be the egress LER in the LSP. (The egress LER is specified at the LSP configuration level with the to command.) When the final node in the path differs from the egress LER, the hop between the final node in the path and the egress LER is treated as a hop to a loose node; that is, standard IP routing is used to determine the path between the final node and the egress LER.

The IP address defines an LSR and can be any interface address or a loopback interface address on the LSR.

The strict and loose parameters are relative to the preceding node. When specifying a loose node, there can be other routers between the previous node and this one. When specifying a strict node, you must make sure that the LSR is actually directly connected to the preceding node.