Enhanced Link Daemon

The enhanced link daemon (enlinkd) discovers connections between nodes using data generated by various link discovery protocols. This data is collected from nodes via SNMP. Enlinkd gathers this data regularly and uses it to generate a snapshot of a device’s neighbors from its perspective, as defined by SNMP data collectors.

The bridge domain discovery process uses the data that the Bridge and IpNetToMedia collectors gather to generate a bridge broadcast domain layout. The bridge forwarding tables (BFTs) that individual nodes provide display information about the MAC addresses discovered on bridge ports. This is what the bridge domain discovery process considers a connection. It is not very useful on its own, so the process also performs domain calculations to assign each MAC address to the port where the device that holds it is effectively connected (the nearest known bridge port).

Connections that the collectors and the bridge domain discovery process find are called "links." These links are discovered based on information that is provided by an agent’s understanding of connections at the OSI Layer 2, Layer 3, or other OSI layers.

In this context, a "link" refers to more than the network OSI Layer 2 connection.

The topologies are made of vertices and edges, and are used to generate a topology map. They also allow the Kafka Producer to send TopologyMessage data.

The following pages describe enlinkd and how to configure it, the supported discovery protocols, and the SNMP MIBs that must be exposed to gather links between nodes. You can view detailed information about a node’s connections and supporting link data on the node detail page in the Horizon web UI.

Topology Layers

The enlinkd topology map supports layered protocol maps.

Click Maps  Topology in the top menu bar to display the topology map, and click the layers symbol in the panel to the right of the map to view layers. The following layers are available:

All (default)

Displays the topology that enlinkd discovers, for all supported protocols (OSPF, IS-IS, Bridge, LLDP, and CDP). This layer also includes user-defined topologies.


Displays the Cisco Discovery Protocol (CDP) topology that enlinkd discovers.


Displays the Link Layer Discovery Protocol (LLDP) topology that enlinkd discovers.


Displays the combined CDP and LLDP topology that enlinkd discovers.


Displays only Bridge links.


Displays the Open Shortest Path First (OSPF) topology that enlinkd discovers.


Displays the Intermediate System to Intermediate System (IS-IS) topology that enlinkd discovers.


Displays the combined OSPF and IS-IS topology that enlinkd discovers.


Displays user-defined topologies.

For more information, see Enlinkd in the Reference section.