diff --git a/firmware/network/rpl_protocol/Makefile b/firmware/network/rpl_protocol/Makefile
index 919941156..c2d95e7e1 100644
--- a/firmware/network/rpl_protocol/Makefile
+++ b/firmware/network/rpl_protocol/Makefile
@@ -1,5 +1,20 @@
-CFLAGS += -DGNRC_RPL_LIFETIME_UNIT=1 -DGNRC_RPL_DEFAULT_LIFETIME=32
+CFLAGS += -DGNRC_RPL_LIFETIME_UNIT=1
+CFLAGS += -DGNRC_RPL_DEFAULT_LIFETIME=32
 CFLAGS += -DGNRC_RPL_REGULAR_DAO_INTERVAL=13
 CFLAGS += -DGNRC_RPL_DEFAULT_DIO_INTERVAL_DOUBLINGS=13
 
+# Currently only supports storing mode. That means, in order to have downwards routes
+# to all nodes the storage space within gnrc_ipv6's Neighbor Information Base must be
+# big enough to store information for each node.
+#
+# For a random topology of n nodes, to ensure you can reach every node from the root,
+# set CONFIG_GNRC_IPV6_NIB_NUMOF == CONFIG_GNRC_IPV6_NIB_OFFL_NUMOF == n.
+# Ref: https://doc.riot-os.org/group__net__gnrc__rpl.html
+CFLAGS += -DCONFIG_GNRC_IPV6_NIB_NUMOF=50
+CFLAGS += -DCONFIG_GNRC_IPV6_NIB_OFFL_NUMOF=50
+
+# Allow alternative parents, increase num of default routers in the NIB.
+# Ref: https://doc.riot-os.org/group__net__gnrc__rpl.html
+CFLAGS += -DCONFIG_GNRC_IPV6_NIB_DEFAULT_ROUTER_NUMOF=2
+
 include $(RIOTBASE)/Makefile.base