The Zenoh Router

For scenarios where peers cannot directly reach each other — different networks, NAT, cloud-to-edge — Zenoh provides a router (zenohd).

Starting the Router

zenohd

By default the router listens on tcp/[::]:7447 and enables multicast scouting on the LAN.

Custom Configuration

Create config.json5:

{
  mode: "router",
  listen: {
    endpoints: ["tcp/0.0.0.0:7447", "udp/0.0.0.0:7447"],
  },
  scouting: {
    multicast: { enabled: true },
  },
}

zenohd --config config.json5

Connecting Clients to the Router

let mut config = zenoh::config::default();
config
    .connect
    .endpoints
    .push("tcp/router.example.com:7447".parse().unwrap());
 
let session = zenoh::open(config).await.unwrap();

Router Topology

Routers are not limited to chains — they can be interconnected in any topology, including mesh networks where each router has multiple peers. Zenoh's link-state routing algorithm automatically computes the optimal path through the graph and reroutes around failures.

A simple chain spanning cloud-to-edge-to-device:

Router chain topology

A mesh of routers across data centres and edge sites:

Router mesh topology

Each hop adds minimal latency. Whether the deployment is a linear chain, a star, or a full mesh, the application code is identical — topology is a configuration concern, not an API concern.

Continue to First Pub/Sub.