diff --git a/configs/README.txt b/configs/README.txt
index 2f393d8535e..bda94884ef1 100644
--- a/configs/README.txt
+++ b/configs/README.txt
@@ -595,6 +595,8 @@ defconfig -- This is a configuration file similar to the Linux
 		CONFIG_NET_RECEIVE_WINDOW - The size of the advertised receiver's
 		  window
 		CONFIG_NET_ARPTAB_SIZE - The size of the ARP table
+        CONFIG_NET_ARP_IPIN - Harvest IP/MAC address mappings from the ARP table
+          from incoming IP packets.
 		CONFIG_NET_BROADCAST - Incoming UDP broadcast support
 		CONFIG_NET_MULTICAST - Outgoing multi-cast address support
 		CONFIG_NET_LLH_LEN - The link level header length