Zero-Cost Hops in Meshtastic

Can a message traverse the mesh across huge distances while burning minimal hop count?

What if you want to send a message or position update from Durban to Mooi River (121 km) at a net cost of only 1 hop?

As of firmware v2.7.11, this is possible using Zero-Cost Hops.

---

What Roles Support Zero-Cost Hops?

Zero-Cost retransmissions apply strictly to nodes configured with the following roles:

• ROUTER
• ROUTER_LATE
• CLIENT_BASE

The 3 Rules for Zero-Cost Retransmissions

A node will relay a packet without decrementing its hop_limit only if:

1. The relaying node's role is ROUTER, ROUTER_LATE, or CLIENT_BASE.
2. The packet is not on its very first hop (the sender was not an edge client).
3. The previous relaying node is set as a Favorite in the receiving node's NodeDB and holds a ROUTER or ROUTER_LATE role.

Zero-Cost Hop Eligibility

Zero-Cost Hops apply only when infrastructure nodes favor each other. To qualify, the relaying node must be configured as a ROUTER, ROUTER_LATE, or CLIENT_BASE, and the preceding relay must be a favorited ROUTER or ROUTER_LATE.

Favoriting Standard Nodes

When any other node role (such as a standard CLIENT or TRACKER) favorites another node, Zero-Cost Hops do not apply. In these cases, marking a node as a favorite strictly protects its details from being deleted from NodeDB during local memory cleanups.

---

Examples

1. Metro Example

We have a ROUTER located at T.B. Davis Flats on a high-rise building in town, and a CLIENT_BASE at Northpoint Flats on a distant building.

• T.B. Davis and Northpoint have favorited each other in their node lists.
• Peter (CLIENT) wants to message Lynn (CLIENT). Both devices are set to a default hop_limit of 3.

Hop	Segment	Cost	Deduction	Remaining hop_limit
1	Peter $\to$ T.B. Davis	Normal (First Hop)	-1	2
2	T.B. Davis $\to$ Northpoint	Zero-Cost (Favorited Router)	0	2
3	Northpoint $\to$ Lynn	Normal	-1	1

Result: Lynn receives the packet with 1 hop remaining, despite the packet traversing two infrastructure relays.

---

2. Cross-Country Example (121 km)

We have a ROUTER at T.B. Davis Flats and three hilltop repeater ROUTER sites at Alverstone, MC02, and EN60.

• Peter (CLIENT in Durban) wants to message Lynn (CLIENT), who has gone on vacation to Mooi River. Both use a default hop_limit of 3.

Favorites Setup (Line of Sight / LOS):

• T.B. Davis favorites Alverstone (LOS).
• Alverstone favorites T.B. Davis, MC02, and EN60 (LOS to all three sites).
• MC02 favorites Alverstone and EN60 (LOS to both sites).
• EN60 favorites MC02 and Alverstone (LOS to both sites).

Hop	Segment	Cost	Deduction	Remaining hop_limit
1	Peter $\to$ T.B. Davis	Normal (First Hop)	-1	2
2	T.B. Davis $\to$ Alverstone	Zero-Cost	0	2
3	Alverstone $\to$ MC02	Zero-Cost	0	2
4	MC02 $\to$ EN60	Zero-Cost	0	2
5	EN60 $\to$ Lynn	Normal	-1	1

Result: The packet travels 121 km across 4 backbone relays, yet Lynn receives the message with 1 hop remaining out of her original 3.

---

Technical Details: Protobuf & MQTT

Protobuf Hop Count Encoding

The hop_limit and hop_start fields are encoded directly inside the MeshPacket Protocol Buffer (Protobuf) structure. This allows every node that receives the packet over the air or via serial/IP/MQTT to read and enforce the exact remaining hop count and original starting distance.

MQTT Integration & Hop Limits

Because Meshtastic transmits raw MeshPacket Protobuf payloads over MQTT, standard hop count rules continue to apply across MQTT connections. Whether a packet received over MQTT qualifies for a Zero-Cost hop depends on whether the receiving or gateway node has favorited the bridging node and whether both satisfy the required ROUTER, ROUTER_LATE, or CLIENT_BASE roles.