Thread Devices Become Unreachable from RPI Over Time Despite Connectivity via ot-ctl about ot-br-posix HOT 2 OPEN

Some observations from the logs:

• There seems to be a high number of routers present on the infra-if network (from the many received RA message). Are they additional Thread Border Routers (BRs).
• The warning log "Received RA from too many routers, ignore RA from fe80:0:0:0:e65f:1ff:fed9:8cd1" suggests you've reached the maximum number of discoverable routers allowed by your configuration. This limit is set by OPENTHREAD_CONFIG_BORDER_ROUTING_MAX_DISCOVERED_ROUTERS.
• The observed behavior is likely a result of this.

You seem to be running an older commit (from 2022). Suggest upgrading to new version. Some specific changes to support larger number of infra-if routers:

• Older implementation published all discovered RIO routes from received RAs in netdata, possibly exhausting the limited Thread netdata space. This has changed to utilize compressed routes in netdata, resulting in significant space savings.
• The RoutingManager now supports heap-allocated data structures. This eliminates the need to pre-configure maximum sizes for discovered routers, prefixes, etc., offering greater flexibility.

from ot-br-posix.

Thank you for your feedback.

In our setup, we have one RCP based border router and 3 other OpenThread devices, which are configured to function as routers within the network. To manage and monitor the state of our OpenThread Border Router (OTBR), we've implemented a script that actively sends messages to these OpenThread devices via UDP. These devices are programmed to respond to these messages, allowing us to ensure continuous communication and validate network stability.

The older commit version we're using might indeed be contributing to the issues. We plan to upgrade to a newer version, keeping in mind the enhancements mentioned, especially regarding netdata space savings and flexible data structures. Upgrading will take some time to observe if the issue reoccurs due to its intermittent nature.

from ot-br-posix.