What is the default data-rate for the RX2 on ABP if i use -1?
# RX2 data-rate
#
# When set to -1, the default RX2 data-rate will be used for the configured
# LoRaWAN band.
#
# Please consult the LoRaWAN Regional Parameters specification for valid
# options of the configured network_server.band.name.
rx2_dr=-1