Configuring LDP

The following example administratively enables LDP for the default network-instance.

--{ * candidate shared default }--[  ]--
# info network-instance default protocols ldp admin-state
    network-instance default {
        protocols {
            ldp {
                admin-state enable
            }
        }
    }

The following example configures LDP neighbor discovery for a network-instance and enables it for a subinterface. The hello-interval parameter specifies the number of seconds between LDP link hello messages. The hello-holdtime parameter specifies how long the LDP link hello adjacency is maintained in the absence of link hello messages from the LDP neighbor.

--{ * candidate shared default }--[  ]--
# info network-instance default protocols ldp discovery
    network-instance default {
        protocols {
            ldp {
                discovery {
                    interfaces {
                        hello-holdtime 30
                        hello-interval 10
                        interface ethernet-1/1.1 {
                            ipv4 {
                                admin-state enable
                            }
                        }
                    }
                }
            }
        }
    }

The following example configures settings for LDP peers:

--{ * candidate shared default }--[  ]--
# info network-instance default protocols ldp peers
    network-instance default {
        protocols {
            ldp {
                peers {
                    session-keepalive-holdtime 240
                    session-keepalive-interval 90
                    }
                    peer 1.1.1.1 label-space-id 1254 {
                        fec-limit 1024
                    }
                }
            }
        }
    }

In this example, the session-keepalive-holdtime parameter specifies the number of seconds an LDP session can remain inactive (no LDP packets received from the peer) before the LDP session is terminated and the corresponding TCP session closed. The session-keepalive-interval parameter specifies the number of seconds between LDP keepalive messages. SR Linux sends LDP keepalive messages at this interval only when no other LDP packets are transmitted over the LDP session.

For an individual LDP peer, indicated by its LSR ID and label space ID, a FEC limit is specified. SR Linux deletes FEC-label bindings received from this peer beyond this limit.

The following example configures LDP to use a dynamic label block named d1. The dynamic label block is configured with a start-label value and an end-label value. See Configuring label blocks for an example of a dynamic label block configuration.

--{ * candidate shared default }--[  ]--
# info network-instance default protocols ldp dynamic-label-block
    network-instance default {
        protocols {
            ldp {
                dynamic-label-block d1
            }
        }
    }

The following example enables longest-prefix match for IPv4 FEC resolution.

--{ * candidate shared default }--[  ]--
# info network-instance default protocols ldp ipv4
    network-instance default {
        protocols {
            ldp {
                ipv4 {
                    fec-resolution {
                        longest-prefix true
                    }
                }
            }
        }
    }

The following example configures the maximum number of next-hops the SR Linux can use for load balancing toward a FEC.

--{ * candidate shared default }--[  ]--
# info network-instance default protocols ldp multipath
    network-instance default {
        protocols {
            ldp {
                multipath {
                    max-paths 64
                }
            }
        }
    }

The following example enables the graceful restart helper capability for LDP.

--{ * candidate shared default }--[  ]--
# info network-instance default protocols ldp graceful--restart
    network-instance default {
        protocols {
            ldp {
                graceful-restart {
                    helper-enable true
                    max-reconnect-time 180
                    max-recovery-time 240
                }
            }
        }
    }

In this example, the max-reconnect-time parameter specifies the number of seconds the SR Linux waits for the remote LDP peer to reconnect after an LDP communication failure. The max-recovery-time parameter specifies the number of seconds the SR Linux router preserves its MPLS forwarding state after receiving the LDP initialization message from the restarted LDP peer.

The following example configures LDP-IGP synchronization for an IS-IS instance.

--{ * candidate shared default }--[  ]--
# info network-instance default protocols isis instance i1 ldp-synchronization
    network-instance default {
        protocols {
            isis {
                instance i1 {
                    ldp-synchronization {
                        hold-down-timer 120
                        end-of-lib true
                    }
                }
            }
        }
    }

In this example, if the LDP adjacency goes down, the IGP increases the metric of the corresponding interface to max-metric. If the adjacency is subsequently reestablished, the IGP waits for the amount of time configured with the hold-down-timer parameter before restoring the normal metric.

When the end-of-lib parameter is set to true, it causes the IGP to restore the normal metric when all label-FEC mappings have been received from the peer, even if time remains in the hold-down timer.