diff --git a/src/core/ipv6/ethip6.c b/src/core/ipv6/ethip6.c
index 1ae784f8..f863d2bb 100644
--- a/src/core/ipv6/ethip6.c
+++ b/src/core/ipv6/ethip6.c
@@ -72,7 +72,7 @@
  *
  * @return
  * - ERR_RTE No route to destination (no gateway to external networks),
- * or the return type of either etharp_query() or ethernet_output().
+ * or the return type of either nd6_queue_packet() or ethernet_output().
  */
 err_t
 ethip6_output(struct netif *netif, struct pbuf *q, const ip6_addr_t *ip6addr)
diff --git a/src/core/netif.c b/src/core/netif.c
index 7ea44829..2d7c8750 100644
--- a/src/core/netif.c
+++ b/src/core/netif.c
@@ -227,7 +227,9 @@ netif_input(struct pbuf *p, struct netif *inp)
  * These functions use netif flags NETIF_FLAG_ETHARP and NETIF_FLAG_ETHERNET
  * to decide whether to forward to ethernet_input() or ip_input().
  * In other words, the functions only work when the netif
- * driver is implemented correctly!
+ * driver is implemented correctly!\n
+ * Members of struct netif should be be initialized by the 
+ * netif init function = netif driver (init parameter of this function).
  *
  * @return netif, or NULL if failed.
  */
diff --git a/src/include/lwip/netif.h b/src/include/lwip/netif.h
index 1d19b27a..6b164b4c 100644
--- a/src/include/lwip/netif.h
+++ b/src/include/lwip/netif.h
@@ -245,17 +245,19 @@ struct netif {
 #if LWIP_IPV4
   /** This function is called by the IP module when it wants
    *  to send a packet on the interface. This function typically
-   *  first resolves the hardware address, then sends the packet. */
+   *  first resolves the hardware address, then sends the packet.
+   *  For ethernet physical layer, this is usually etharp_output() */
   netif_output_fn output;
 #endif /* LWIP_IPV4 */
-  /** This function is called by the ARP module when it wants
+  /** This function is called by ethernet_output() when it wants
    *  to send a packet on the interface. This function outputs
    *  the pbuf as-is on the link medium. */
   netif_linkoutput_fn linkoutput;
 #if LWIP_IPV6
   /** This function is called by the IPv6 module when it wants
    *  to send a packet on the interface. This function typically
-   *  first resolves the hardware address, then sends the packet. */
+   *  first resolves the hardware address, then sends the packet.
+   *  For ethernet physical layer, this is usually ethip6_output() */
   netif_output_ip6_fn output_ip6;
 #endif /* LWIP_IPV6 */
 #if LWIP_NETIF_STATUS_CALLBACK