diff --git a/core/net/rpl/rpl-dag.c b/core/net/rpl/rpl-dag.c
index 0150e093a..220d9facc 100644
--- a/core/net/rpl/rpl-dag.c
+++ b/core/net/rpl/rpl-dag.c
@@ -106,6 +106,20 @@ static void
 rpl_set_preferred_parent(rpl_dag_t *dag, rpl_parent_t *p)
 {
   if(dag != NULL && dag->preferred_parent != p) {
+    PRINTF("RPL: rpl_set_preferred_parent ");
+    if(p != NULL) {
+      PRINT6ADDR(rpl_get_parent_ipaddr(p));
+    } else {
+      PRINTF("NULL");
+    }
+    PRINTF(" used to be ");
+    if(dag->preferred_parent != NULL) {
+      PRINT6ADDR(rpl_get_parent_ipaddr(dag->preferred_parent));
+    } else {
+      PRINTF("NULL");
+    }
+    PRINTF("\n");
+
     /* Always keep the preferred parent locked, so it remains in the
      * neighbor table. */
     nbr_table_unlock(rpl_parents, dag->preferred_parent);
@@ -288,11 +302,13 @@ rpl_repair_root(uint8_t instance_id)
   instance = rpl_get_instance(instance_id);
   if(instance == NULL ||
      instance->current_dag->rank != ROOT_RANK(instance)) {
+    PRINTF("RPL: rpl_repair_root triggered but not root\n");
     return 0;
   }
 
   RPL_LOLLIPOP_INCREMENT(instance->current_dag->version);
   RPL_LOLLIPOP_INCREMENT(instance->dtsn_out);
+  PRINTF("RPL: rpl_repair_root initiating global repair with version %d\n", instance->current_dag->version);
   rpl_reset_dio_timer(instance);
   return 1;
 }
@@ -514,6 +530,7 @@ rpl_add_parent(rpl_dag_t *dag, rpl_dio_t *dio, uip_ipaddr_t *addr)
    * Typically, the parent is added upon receiving a DIO. */
   uip_lladdr_t *lladdr = uip_ds6_nbr_lladdr_from_ipaddr(addr);
 
+  PRINTF("RPL: rpl_add_parent lladdr %p\n", lladdr);
   if(lladdr != NULL) {
     /* Add parent in rpl_parents */
     p = nbr_table_add_lladdr(rpl_parents, (rimeaddr_t *)lladdr);
@@ -990,6 +1007,7 @@ global_repair(uip_ipaddr_t *from, rpl_dag_t *dag, rpl_dio_t *dio)
   } else {
     dag->rank = dag->instance->of->calculate_rank(p, 0);
     dag->min_rank = dag->rank;
+    PRINTF("RPL: rpl_process_parent_event global repair\n");
     rpl_process_parent_event(dag->instance, p);
   }
 
@@ -1031,6 +1049,7 @@ rpl_recalculate_ranks(void)
   while(p != NULL) {
     if(p->dag != NULL && p->dag->instance && p->updated) {
       p->updated = 0;
+      PRINTF("RPL: rpl_process_parent_event recalculate_ranks\n");
       if(!rpl_process_parent_event(p->dag->instance, p)) {
         PRINTF("RPL: A parent was dropped\n");
       }
@@ -1210,7 +1229,7 @@ rpl_process_dio(uip_ipaddr_t *from, rpl_dio_t *dio)
   PRINTF(", rank %u, min_rank %u, ",
 	 instance->current_dag->rank, instance->current_dag->min_rank);
   PRINTF("parent rank %u, parent etx %u, link metric %u, instance etx %u\n",
-	 p->rank, p->mc.obj.etx, p->link_metric, instance->mc.obj.etx);
+	 p->rank, -1/*p->mc.obj.etx*/, p->link_metric, instance->mc.obj.etx);
 
   /* We have allocated a candidate parent; process the DIO further. */
 
diff --git a/core/net/rpl/rpl-icmp6.c b/core/net/rpl/rpl-icmp6.c
index dee62fcff..2b9c87476 100644
--- a/core/net/rpl/rpl-icmp6.c
+++ b/core/net/rpl/rpl-icmp6.c
@@ -663,8 +663,13 @@ dao_input(void)
   rep = uip_ds6_route_lookup(&prefix);
 
   if(lifetime == RPL_ZERO_LIFETIME) {
+    PRINTF("RPL: No-Path DAO received\n");
     /* No-Path DAO received; invoke the route purging routine. */
-    if(rep != NULL && rep->state.nopath_received == 0 && rep->length == prefixlen && uip_ipaddr_cmp(uip_ds6_route_nexthop(rep), &dao_sender_addr)) {
+    if(rep != NULL &&
+       rep->state.nopath_received == 0 &&
+       rep->length == prefixlen &&
+       uip_ds6_route_nexthop(rep) != NULL &&
+       uip_ipaddr_cmp(uip_ds6_route_nexthop(rep), &dao_sender_addr)) {
       PRINTF("RPL: Setting expiration timer for prefix ");
       PRINT6ADDR(&prefix);
       PRINTF("\n");
@@ -677,12 +682,15 @@ dao_input(void)
   learned_from = uip_is_addr_mcast(&dao_sender_addr) ?
                  RPL_ROUTE_FROM_MULTICAST_DAO : RPL_ROUTE_FROM_UNICAST_DAO;
 
+  PRINTF("RPL: DAO from %s\n",
+         learned_from == RPL_ROUTE_FROM_UNICAST_DAO? "unicast": "multicast");
   if(learned_from == RPL_ROUTE_FROM_UNICAST_DAO) {
     /* Check whether this is a DAO forwarding loop. */
     p = rpl_find_parent(dag, &dao_sender_addr);
     /* check if this is a new DAO registration with an "illegal" rank */
     /* if we already route to this node it is likely */
-    if(p != NULL && DAG_RANK(p->rank, instance) < DAG_RANK(dag->rank, instance)) {
+    if(p != NULL &&
+       DAG_RANK(p->rank, instance) < DAG_RANK(dag->rank, instance)) {
       PRINTF("RPL: Loop detected when receiving a unicast DAO from a node with a lower rank! (%u < %u)\n",
           DAG_RANK(p->rank, instance), DAG_RANK(dag->rank, instance));
       p->rank = INFINITE_RANK;
@@ -691,6 +699,7 @@ dao_input(void)
     }
   }
 
+  PRINTF("RPL: adding DAO route\n");
   rep = rpl_add_route(dag, &prefix, prefixlen, &dao_sender_addr);
   if(rep == NULL) {
     RPL_STAT(rpl_stats.mem_overflows++);
@@ -704,7 +713,7 @@ dao_input(void)
   if(learned_from == RPL_ROUTE_FROM_UNICAST_DAO) {
     if(dag->preferred_parent) {
       PRINTF("RPL: Forwarding DAO to parent ");
-      PRINT6ADDR(&dag->preferred_parent->addr);
+      PRINT6ADDR(rpl_get_parent_ipaddr(dag->preferred_parent));
       PRINTF("\n");
       uip_icmp6_send(rpl_get_parent_ipaddr(dag->preferred_parent),
                      ICMP6_RPL, RPL_CODE_DAO, buffer_length);
@@ -789,7 +798,7 @@ dao_output_target(rpl_parent_t *parent, uip_ipaddr_t *prefix, uint8_t lifetime)
   PRINTF("RPL: Sending DAO with prefix ");
   PRINT6ADDR(prefix);
   PRINTF(" to ");
-  PRINT6ADDR(&parent->addr);
+  PRINT6ADDR(rpl_get_parent_ipaddr(parent));
   PRINTF("\n");
 
   uip_icmp6_send(rpl_get_parent_ipaddr(parent), ICMP6_RPL, RPL_CODE_DAO, pos);
diff --git a/core/net/rpl/rpl.c b/core/net/rpl/rpl.c
index cf01c286a..4ff9b1c6a 100644
--- a/core/net/rpl/rpl.c
+++ b/core/net/rpl/rpl.c
@@ -183,6 +183,7 @@ rpl_link_neighbor_callback(const rimeaddr_t *addr, int status, int numtx)
       parent = rpl_find_parent_any_dag(instance, &ipaddr);
       if(parent != NULL) {
         /* Trigger DAG rank recalculation. */
+        PRINTF("RPL: rpl_link_neighbor_callback triggering update\n");
         parent->updated = 1;
         if(instance->of->neighbor_link_callback != NULL) {
           instance->of->neighbor_link_callback(parent, status, numtx);
@@ -208,6 +209,7 @@ rpl_ipv6_neighbor_callback(uip_ds6_nbr_t *nbr)
       if(p != NULL) {
         p->rank = INFINITE_RANK;
         /* Trigger DAG rank recalculation. */
+        PRINTF("RPL: rpl_ipv6_neighbor_callback infinite rank\n");
         p->updated = 1;
       }
     }
diff --git a/core/net/uip-debug.c b/core/net/uip-debug.c
index bc611f383..9a4f0cb48 100644
--- a/core/net/uip-debug.c
+++ b/core/net/uip-debug.c
@@ -43,6 +43,10 @@
 void
 uip_debug_ipaddr_print(const uip_ipaddr_t *addr)
 {
+  if(addr == NULL || addr->u8 == NULL) {
+    printf("(NULL IP addr)");
+    return;
+  }
 #if UIP_CONF_IPV6
   uint16_t a;
   unsigned int i;