MeshCore Routing: Flood-First, Direct-Route-After

This page describes MeshCore's routing mechanism as verified from 
docs/packet_format.md (for the packet/route-type structure) and the firmware source and CLI docs (for the routing behaviour) in the official MeshCore repository. Note: MeshCore's hybrid flood/direct scheme is not the AODV protocol - earlier versions of this page incorrectly used AODV terminology (path discovery/acknowledgment), which does not match how MeshCore works.
How MeshCore Routing Actually Works
MeshCore uses a flood-first, direct-route-after mechanism:
Step 1: Flood Routing (First Message)
When a node sends a message to a destination it has no path for, the packet uses 
ROUTE_TYPE_FLOOD. Every repeater in range re-broadcasts the packet (subject to flood limits); Companion/client nodes do not repeat. The destination node receives the message through whatever path it arrived on.
Step 2: Path Return
The destination node responds by sending back a 
PAYLOAD_TYPE_PATH packet. This packet contains the complete list of repeaters through which the original flooded message arrived. The path travels back to the original sender.
Step 3: Direct Routing (Subsequent Messages)
Armed with the learned path, the sender now uses 
ROUTE_TYPE_DIRECT for subsequent messages. The packet embeds the repeater list, and only those specific repeaters forward it. All other repeaters ignore the packet entirely.
Why This Is More Efficient Than Pure Flooding
 
After the initial flood, all subsequent messages in a conversation use direct routing - dramatically less channel airtime
 
A busy network with many established conversations generates far less channel overhead than a pure flood mesh
 
Path re-learning happens automatically if a direct-routed message fails (falls back to flood)
Route Types Reference
Route Type
When Used
ROUTE_TYPE_FLOOD
Initial contact; all group/channel messages
ROUTE_TYPE_DIRECT
Point-to-point after path is known
ROUTE_TYPE_TRANSPORT_FLOOD
Flood with regional transport code
ROUTE_TYPE_TRANSPORT_DIRECT
Direct-routed with regional transport code
Source: docs/packet_format.md (route-type table and packet structure) plus the firmware source (Mesh.cpp) and CLI docs (path-return and re-learning behaviour) in the official MeshCore repository. Verified 2026-05-03.