Skip to content
Documentation Prelude Topology Engine 1.0.0

Nodes

The fields Prelude TE surfaces on each node in the consolidated topology, including SR-MPLS capabilities, SRv6 locators, and Flex-Algo participation.

A node in the topology is a network element — usually a router, sometimes a pseudonode created for multi-access links — that one of your BGP-LS peers reported on. This page documents every field the engine surfaces on a node, in the order you see it in the export.

Example payload

A realistic node export from a small Flex-Algo-enabled fabric. SR-MPLS capabilities and Node SIDs, SRv6 capabilities and locators, and Flex-Algo participation all appear inline on the same object.

{
  "key": "ASN:64001/BGPLS:100/IGP:0001.0000.0001",
  "safe-id": "ASN_64001_BGPLS_100_IGP_0001_0000_0001",
  "instance-id": 100,
  "name": "dev-core-1",
  "router-id": "0001.0000.0001",
  "te-router-id": "10.1.1.1",
  "asn": 64001,
  "protocol-id": 2,
  "area-id": "0",
  "is-pseudonode": false,
  "sr-mpls": {
    "capabilities": {
      "ipv4-supported": true,
      "ipv6-supported": false,
      "srgb-base": 16000,
      "srgb-range": 8000,
      "srlb-base": 15000,
      "srlb-range": 1000
    },
    "node-sids": [
      { "prefix": "10.1.1.1/32", "index": 1,    "sid": 16001, "algorithm": 0 },
      { "prefix": "10.1.1.1/32", "index": 1001, "sid": 17001, "algorithm": 128 }
    ]
  },
  "flex-algo": {
    "algorithms": [0, 1, 128],
    "definitions": [
      {
        "algorithm": 128,
        "metric-type": 0,
        "metric-type-name": "IGP",
        "calc-type": 0,
        "calc-type-name": "SPF",
        "priority": 128,
        "exclude-any": 32,
        "exclude-any-bits": [5]
      }
    ]
  },
  "srv6": {
    "capabilities": { "oam": false },
    "locators": [
      { "locator": "fcdd:dd01:1::/48", "algorithm": 128 },
      { "locator": "fcdd:dd00:1::/48", "algorithm": 0 }
    ]
  },
  "outgoing-links": 10,
  "incoming-links": 10,
  "prefix-count": 12,
  "source-peers": ["172.31.0.200", "172.31.0.100"],
  "last-update": "2026-05-26T11:22:45.595261+02:00"
}

Identity

Each node carries identifiers used by the UI, the API, and any output:

  • key — canonical identifier of the form ASN:<asn>/BGPLS:<instance-id>/IGP:<router-id>. Unique within a domain.
  • safe-id — an HTML/URL-safe variant of the key, used by the UI in routes.
  • instance-id — the BGP-LS Instance Identifier the node was advertised under. Same as the domain.

Routing identity

  • name — the node name advertised in BGP-LS, when available.
  • router-id — the IGP Router ID extracted from the node descriptor.
  • te-router-id — the TE Router ID (IPv4) from the node attributes TLV (1028), when advertised.
  • te-router-id-v6 — the TE Router ID (IPv6) from the node attributes TLV (1029), when advertised.
  • asn — the AS number the node belongs to.
  • protocol-id — numeric protocol identifier the node was learned from. 1 ISIS L1, 2 ISIS L2, 3 OSPFv2, 6 OSPFv3, etc.
  • area-id — the area or domain identifier carried with the node.
  • is-pseudonode — true for multi-access pseudonodes, false for real routers.

Aggregate counters

  • outgoing-links / incoming-links — number of links currently in the graph with this node as their local or remote end.
  • prefix-count — number of prefixes currently attached to this node.

These are computed from the in-memory graph and update live as the topology moves.

Source peers and last update

  • source-peers — the list of BGP-LS speakers currently contributing this node. A list of one means single-source; longer lists mean the node is redundantly fed.
  • last-update — timestamp of the most recent change that produced the current payload.

SR-MPLS

If the node advertises SR-MPLS (RFC 8667), the export carries an sr-mpls block:

  • capabilities:
    • ipv4-supported (I-flag) and ipv6-supported (V-flag) — which MPLS data planes the node supports.
    • srgb-base / srgb-range — the SR Global Block, used for Prefix SIDs.
    • srlb-base / srlb-range — the SR Local Block, used for Adjacency SIDs (when advertised).
  • node-sids — one entry per Prefix SID advertised with the N-flag set (typically a loopback). Each entry has:
    • prefix — the source prefix (e.g. 10.1.1.1/32).
    • index — the SID index from the IGP.
    • sid — the computed MPLS label (index + SRGB base).
    • algorithm — 0 plain SPF, 1 Strict-SPF, 128–255 Flex-Algo Node SID.

SRv6

If the node advertises SRv6 (RFC 9514), the export carries an srv6 block:

  • capabilities.oam — true when the node can process SRv6 OAM packets (O-flag of the SRv6 Capabilities TLV).
  • locators — one entry per locator advertised by the node:
    • locator — the IPv6 prefix used as the locator (e.g. fcdd:dd01:1::/48).
    • algorithm — same scale as SR-MPLS Node SIDs.

A node typically advertises one locator per algorithm it participates in.

Flex-Algo

If the node participates in Flex-Algo (RFC 9350), the export carries a flex-algo block with the list of algorithms it participates in and, for the algorithms it is advertising, the corresponding FAD. See Flex-Algo for the detailed field reference and the cross-cutting algorithm field.

Filtering by: