diff --git a/core/contiki-default-conf.h b/core/contiki-default-conf.h
index df7fe9e6d..0083f7e10 100644
--- a/core/contiki-default-conf.h
+++ b/core/contiki-default-conf.h
@@ -192,10 +192,24 @@
 #define NBR_TABLE_CONF_MAX_NEIGHBORS 8
 #endif /* NBR_TABLE_CONF_MAX_NEIGHBORS */
 
+/* UIP_CONF_ND6_SEND_RA enables standard IPv6 Router Advertisement.
+ * We enable it by default when IPv6 is used without RPL. */
+#ifndef UIP_CONF_ND6_SEND_RA
+#define UIP_CONF_ND6_SEND_RA (NETSTACK_CONF_WITH_IPV6 && !UIP_CONF_IPV6_RPL)
+#endif /* UIP_CONF_ND6_SEND_RA */
+
 /* UIP_CONF_ND6_SEND_NA enables standard IPv6 Neighbor Discovery Protocol.
-   This is unneeded when RPL is used. Disable to save ROM and a little RAM. */
+   We enable it by default when IPv6 is used without RPL.
+   With RPL, the neighbor cache (link-local IPv6 <-> MAC address mapping)
+   is fed whenever receiving DIO and DAO messages. This is always sufficient
+   for RPL routing, i.e. to send to the preferred parent or any child.
+   Link-local unicast to other neighbors may, however, not be possible if
+   we never receive any DIO from them. This may happen if the link from the
+   neighbor to us is weak, if DIO transmissions are suppressed (Trickle
+   timer) or if the neighbor chooses not to transmit DIOs because it is
+   a leaf node or for any reason. */
 #ifndef UIP_CONF_ND6_SEND_NA
-#define UIP_CONF_ND6_SEND_NA 1
+#define UIP_CONF_ND6_SEND_NA (NETSTACK_CONF_WITH_IPV6 && !UIP_CONF_IPV6_RPL)
 #endif /* UIP_CONF_ND6_SEND_NA */
 
 /*---------------------------------------------------------------------------*/
diff --git a/examples/cc2530dk/udp-ipv6/project-conf.h b/examples/cc2530dk/udp-ipv6/project-conf.h
index fb37ebfc3..adb4fc0f0 100644
--- a/examples/cc2530dk/udp-ipv6/project-conf.h
+++ b/examples/cc2530dk/udp-ipv6/project-conf.h
@@ -45,5 +45,6 @@
 #define BUTTON_SENSOR_CONF_ON 1
 #define UIP_CONF_ICMP6        1
 #define RIMESTATS_CONF_ENABLED 1
+#define UIP_CONF_ND6_SEND_NA 1
 
 #endif /* PROJECT_CONF_H_ */
diff --git a/examples/cc2538dk/udp-ipv6-echo-server/Makefile b/examples/cc2538dk/udp-ipv6-echo-server/Makefile
index 32b3ca79f..4988d0b52 100644
--- a/examples/cc2538dk/udp-ipv6-echo-server/Makefile
+++ b/examples/cc2538dk/udp-ipv6-echo-server/Makefile
@@ -4,4 +4,5 @@ all: $(CONTIKI_PROJECT)
 
 CONTIKI = ../../..
 CONTIKI_WITH_IPV6 = 1
+CFLAGS += -DUIP_CONF_ND6_SEND_NA=1
 include $(CONTIKI)/Makefile.include
diff --git a/examples/sensinode/udp-ipv6/project-conf.h b/examples/sensinode/udp-ipv6/project-conf.h
index 4e74d406e..bb755aee9 100644
--- a/examples/sensinode/udp-ipv6/project-conf.h
+++ b/examples/sensinode/udp-ipv6/project-conf.h
@@ -47,5 +47,6 @@
 #define BUTTON_SENSOR_CONF_ON 1
 #define RIMESTATS_CONF_ENABLED 1
 #define VIZTOOL_CONF_ON         0
+#define UIP_CONF_ND6_SEND_NA 1
 
 #endif /* PROJECT_CONF_H_ */
diff --git a/examples/udp-ipv6/Makefile b/examples/udp-ipv6/Makefile
index 62118cb49..7a38bdbc5 100644
--- a/examples/udp-ipv6/Makefile
+++ b/examples/udp-ipv6/Makefile
@@ -2,4 +2,5 @@ all: udp-server udp-client
 
 CONTIKI = ../..
 CONTIKI_WITH_IPV6 = 1
+CFLAGS += -DUIP_CONF_ND6_SEND_NA=1
 include $(CONTIKI)/Makefile.include
diff --git a/regression-tests/11-ipv6/code/receiver/project-conf.h b/regression-tests/11-ipv6/code/receiver/project-conf.h
index 877ed0ac4..17a25e129 100644
--- a/regression-tests/11-ipv6/code/receiver/project-conf.h
+++ b/regression-tests/11-ipv6/code/receiver/project-conf.h
@@ -1,4 +1,5 @@
-
+#undef UIP_CONF_ND6_SEND_NA
+#define UIP_CONF_ND6_SEND_NA 1
 
 #ifdef BUFSIZE
 #undef UIP_CONF_BUFFER_SIZE
diff --git a/regression-tests/11-ipv6/code/sender/project-conf.h b/regression-tests/11-ipv6/code/sender/project-conf.h
index 877ed0ac4..17a25e129 100644
--- a/regression-tests/11-ipv6/code/sender/project-conf.h
+++ b/regression-tests/11-ipv6/code/sender/project-conf.h
@@ -1,4 +1,5 @@
-
+#undef UIP_CONF_ND6_SEND_NA
+#define UIP_CONF_ND6_SEND_NA 1
 
 #ifdef BUFSIZE
 #undef UIP_CONF_BUFFER_SIZE