MPLS

Enabling MPLS

MPLS label processing is per-interface. Enable it on each interface that should accept labeled packets:

interface {
    ethernet eth0 {
        unit 0 {
            mpls {
                enable true
            }
        }
    }
}

This sets net.mpls.conf.eth0.input=1. The global label-table size is governed by the net.mpls.platform_labels sysctl (configure it via the sysctl {} block; it defaults to off, which disables MPLS entirely).

The Linux kernel must have the mpls_router and mpls_iptunnel modules loaded. ze doctor warns (doctor-mpls-unavailable) when they are missing.

Inspecting the forwarding table

ze show mpls forwarding              # all installed MPLS entries
ze show mpls forwarding limit 500    # cap the response size

Each row reports the incoming label (in-label), the operation (swap or pop), any outgoing out-labels, the next-hop, and the egress device. The data is read directly from the kernel AF_MPLS routing table.

Metrics

• ze_fibkernel_mpls_routes_installed -- current MPLS labeled-route count.
• ze_fibkernel_mpls_installs_total -- MPLS routes successfully programmed.

Label distribution

Two label-distribution protocols are available (both experimental):

• LDP (RFC 5036) for IGP-shortest-path label distribution.
• RSVP-TE (RFC 3209) for traffic-engineered explicit-path LSPs with bandwidth reservation -- see RSVP-TE.

LDP configuration

ldp {
    lsr-id 10.0.0.1
    transport-address 10.0.0.1
    interfaces eth0
    interfaces eth1
}

• lsr-id -- this router's LSR identifier (IPv4 address format).
• transport-address -- address advertised for the LDP TCP session.
• interfaces -- a list entry per interface on which LDP Hello discovery runs (repeat the leaf for each interface).
• hello-interval / hello-hold-time / keepalive-time -- optional soft-state timers (defaults 5s / 15s / 60s).

Inspect LDP state with show ldp neighbor (session state, transport address) and show ldp binding (FEC-to-label bindings). A label binding learned from a neighbor programs an ingress push entry in the kernel MPLS FIB toward that neighbor.