How Automatic Return Routing solves IP overlap

Cloudflare introduced Automatic Return Routing in Closed Beta, aRR is available as an optional tool for Cloudflare One customers.

Automatic Return Routing routes return traffic to the tunnel that initiated the flow without consulting the routing table, aRR records the initiating tunnel when a flow is set up and uses that to return traffic.

Uses stateful tracking of flows, aRR stores flow state and the initiating tunnel in memory to maintain symmetric return.

Private networks can have overlapping IP address spaces duplication arises in mergers, extranets, and uniform branch architectures.

Traditional fixes include VRF and NAT and introduce administrative overhead, vRF requires virtual routing tables and route leaking; NAT requires per-site address mapping.