SR-MPLS configuration on the default network-instance

Segment routing on the MPLS data plane is supported on the default network-instance only. To configure available SR-MPLS options for the default network-instance, perform the following tasks:

  1. Defining the SRGB and enabling SR-MPLS
  2. (Optional) Defining protocol-independent prefix SIDs

Defining the SRGB and enabling SR-MPLS

The SRGB references a static shared MPLS label range that must be one contiguous block of labels. To configure the SRGB, you must enter the segment-routing mpls context on the default network-instance, which enables SR-MPLS.

Note: Nokia strongly recommends to use identical SRGBs on all nodes within the SR domain.
  1. Define a static MPLS label range in the system context.
  2. Assign that MPLS label range to be available for use by the SRGB.

Define the MPLS label range for the SRGB

The following example defines static shared MPLS label range srgb-range-1 for the SRGB. 

--{ * candidate shared default }--[ ]--
# info system mpls label-ranges static srgb-range-1
    system {
        mpls {
            label-ranges {
                static srgb-range-1 {
                    shared true
                    start-label 16001
                    end-label 16999
                }
            }
        }
    }

Assign the MPLS label range to the SRGB

The following example assigns static label range srgb-range-1 to the SRGB. 

--{ * candidate shared default }--[ ]--
# info network-instance default segment-routing mpls global-block
    network-instance default {
        segment-routing {
            mpls {
                global-block {
                    label-range srgb-range-1
                }
            }
        }
    }

Defining protocol-independent prefix SIDs

You can configure a prefix SID that is shared by multiple IGPs (currently only IS-IS) in a network-instance. SR Linux supports up to four protocol-independent prefix SIDs to be associated with the default network-instance. By default, all prefix SIDs are set as node SIDs. However, you can disable the node SID flag as required.

Note: As an alternative, you can define a node SID under the IS-IS configuration context. In that case, the node SID is not protocol-independent, but is specific to that IGP. However, in that case the node SID flag cannot be disabled.

A single interface can be configured with both an IS-IS node SID and a protocol-independent prefix SID. In this case, the IS-IS IGP overrides the protocol independent prefix SID configuration, and only the IGP node SID is advertised.

A protocol-independent prefix SID is typically preferred over an IS-IS node SID because the protocol-independent prefix SID provides more flexibility. If required, you can override the protocol-independent prefix SID with an IGP node SID.

  • Configure the primary address of a loopback (loN.n) or system0.0 subinterface with the required node SID prefix.
  1. To configure the local prefix SID, you must specify the following:
    • The local-prefix SID index (1 to 4).
    • The loopback subinterface that owns the advertised prefixes.
    • The IPv4 or IPv6 (or both) label index for the SID, referencing the SRGB base, using one of the following options:

      ipv4-label-index | ipv6-label-index

  2. Optionally, you can disable the node SID flag on the defined prefix SID, using the following option:
    node-sid {true | false}

    If the referenced interface is system0.0, the node SID flag cannot be set to false.

Define local prefix SID

The following example defines local prefix SID 2 on loopback interface lo0.2. Prefix SID 2 is associated with IPv4 label index 102 and IPv6 label index 202, and the node SID flag is set to false.

--{ * candidate shared default }--[ ]--
# info network-instance default segment-routing mpls local-prefix-sid 2
    network-instance default {
        segment-routing {
            mpls {
                local-prefix-sid 2 {
                    interface lo0.2
                    ipv4-label-index 102
                    ipv6-label-index 202
                    node-sid false
                }
            }
        }
    }