Hi Simon, Sven, Thank you very much for your help. Our batman-adv BATMAN_IV are deployed in 100+ (may be more) sites, and works almost perfectly. There is a minor issue: after reboot the board, sometimes it takes several minutes to join mesh after reboot when there are <4 nodes in the network. - Usually board joins mesh instantly. - When this happens, I can still 'ping ip-address%mesh0' using IBSS interface, so it is likely a batman-adv issue. - This does not happen when I have >=4 nodes in the mesh network.   -- For a setup of 6 nodes, I run the automated test for 1000 cycles, and no issues. I use the automated test: - reboot one board, and sleep 20 seconds - 'batctl n | tail -1 | grep mesh0' to see if it is empty. Here is my environment: - Atheros ar9331 MIPS platform + built-in ath9k WiFi - OpenWRT tag 15.05 - batman-adv version 2016.1.3 (with 22 patches in patches/ subfolder as you know it very well) - routing_algos = BATMAN_IV Is this a known issue? Thanks again. Xuebing Wang