diff --git a/staticlibs/testutils/devicetests/com/android/testutils/RouterAdvertisementResponder.java b/staticlibs/testutils/devicetests/com/android/testutils/RouterAdvertisementResponder.java
index 4ad93d8..91c3f76 100644
--- a/staticlibs/testutils/devicetests/com/android/testutils/RouterAdvertisementResponder.java
+++ b/staticlibs/testutils/devicetests/com/android/testutils/RouterAdvertisementResponder.java
@@ -18,12 +18,14 @@
 
 import static android.system.OsConstants.IPPROTO_ICMPV6;
 
-import static com.android.net.module.util.NetworkStackConstants.ETHER_ADDR_LEN;
-import static com.android.net.module.util.NetworkStackConstants.ETHER_SRC_ADDR_OFFSET;
 import static com.android.net.module.util.NetworkStackConstants.ETHER_TYPE_IPV6;
+import static com.android.net.module.util.NetworkStackConstants.ICMPV6_ND_OPTION_TLLA;
+import static com.android.net.module.util.NetworkStackConstants.ICMPV6_NEIGHBOR_SOLICITATION;
 import static com.android.net.module.util.NetworkStackConstants.ICMPV6_ROUTER_SOLICITATION;
 import static com.android.net.module.util.NetworkStackConstants.IPV6_ADDR_ALL_NODES_MULTICAST;
-import static com.android.net.module.util.NetworkStackConstants.IPV6_ADDR_ALL_ROUTERS_MULTICAST;
+import static com.android.net.module.util.NetworkStackConstants.NEIGHBOR_ADVERTISEMENT_FLAG_OVERRIDE;
+import static com.android.net.module.util.NetworkStackConstants.NEIGHBOR_ADVERTISEMENT_FLAG_ROUTER;
+import static com.android.net.module.util.NetworkStackConstants.NEIGHBOR_ADVERTISEMENT_FLAG_SOLICITED;
 import static com.android.net.module.util.NetworkStackConstants.PIO_FLAG_AUTONOMOUS;
 import static com.android.net.module.util.NetworkStackConstants.PIO_FLAG_ON_LINK;
 
@@ -31,6 +33,7 @@
 import android.net.IpPrefix;
 import android.net.LinkAddress;
 import android.net.MacAddress;
+import android.util.ArrayMap;
 import android.util.Pair;
 
 import com.android.net.module.util.Ipv6Utils;
@@ -38,18 +41,19 @@
 import com.android.net.module.util.structs.EthernetHeader;
 import com.android.net.module.util.structs.Icmpv6Header;
 import com.android.net.module.util.structs.Ipv6Header;
+import com.android.net.module.util.structs.LlaOption;
+import com.android.net.module.util.structs.NsHeader;
 import com.android.net.module.util.structs.PrefixInformationOption;
 import com.android.net.module.util.structs.RdnssOption;
 
 import java.io.IOException;
 import java.net.Inet6Address;
 import java.nio.ByteBuffer;
-import java.util.ArrayList;
-import java.util.Arrays;
-import java.util.List;
+import java.util.Map;
 
 /**
- * RA responder class useful for tests that require a provisioned interface.
+ * ND (RA & NA) responder class useful for tests that require a provisioned IPv6 interface.
+ * TODO: rename to NdResponder
  */
 public class RouterAdvertisementResponder extends PacketResponder {
     private static final String TAG = "RouterAdvertisementResponder";
@@ -57,26 +61,28 @@
     private static final Inet6Address DNS_SERVER =
             (Inet6Address) InetAddresses.parseNumericAddress("2001:4860:4860::64");
     private final TapPacketReader mPacketReader;
-    private final List<Pair<MacAddress, Inet6Address>> mRouterList = new ArrayList<>();
+    // Maps IPv6 address to MacAddress and isRouter boolean.
+    private final Map<Inet6Address, Pair<MacAddress, Boolean>> mNeighborMap = new ArrayMap<>();
 
     public RouterAdvertisementResponder(TapPacketReader packetReader) {
-        super(packetReader, RouterAdvertisementResponder::isRouterSolicitation, TAG);
+        super(packetReader, RouterAdvertisementResponder::isRsOrNs, TAG);
         mPacketReader = packetReader;
     }
 
-    private static boolean isRouterSolicitation(byte[] packet) {
+    /** Returns true if the packet is a router solicitation or neighbor solicitation message. */
+    private static boolean isRsOrNs(byte[] packet) {
         final ByteBuffer buffer = ByteBuffer.wrap(packet);
         final EthernetHeader ethHeader = Struct.parse(EthernetHeader.class, buffer);
         if (ethHeader.etherType != ETHER_TYPE_IPV6) {
             return false;
         }
         final Ipv6Header ipv6Header = Struct.parse(Ipv6Header.class, buffer);
-        if (ipv6Header.nextHeader != IPPROTO_ICMPV6
-                || !ipv6Header.dstIp.equals(IPV6_ADDR_ALL_ROUTERS_MULTICAST)) {
+        if (ipv6Header.nextHeader != IPPROTO_ICMPV6) {
             return false;
         }
         final Icmpv6Header icmpv6Header = Struct.parse(Icmpv6Header.class, buffer);
-        return icmpv6Header.type == ICMPV6_ROUTER_SOLICITATION;
+        return icmpv6Header.type == ICMPV6_ROUTER_SOLICITATION
+            || icmpv6Header.type == ICMPV6_NEIGHBOR_SOLICITATION;
     }
 
     /**
@@ -85,7 +91,16 @@
      * @param ip the link-local address of the router.
      */
     public void addRouterEntry(MacAddress mac, Inet6Address ip) {
-        mRouterList.add(new Pair<>(mac, ip));
+        mNeighborMap.put(ip, new Pair<>(mac, true));
+    }
+
+    /**
+     * Adds a new neighbor to be advertised.
+     * @param mac the mac address of the neighbor.
+     * @param ip the link-local address of the neighbor.
+     */
+    public void addNeighborEntry(MacAddress mac, Inet6Address ip) {
+        mNeighborMap.put(ip, new Pair<>(mac, false));
     }
 
     private ByteBuffer buildPrefixOption() {
@@ -105,19 +120,59 @@
                 0/*retransTimer, unspecified*/, buildPrefixOption(), buildRdnssOption());
     }
 
+    private static void sendResponse(TapPacketReader reader, ByteBuffer buffer) {
+        try {
+            reader.sendResponse(buffer);
+        } catch (IOException e) {
+            throw new RuntimeException("Failed to send buffer.");
+        }
+    }
+
+    private void replyToRouterSolicitation(TapPacketReader reader, MacAddress dstMac) {
+        for (Map.Entry<Inet6Address, Pair<MacAddress, Boolean>> it : mNeighborMap.entrySet()) {
+            final boolean isRouter = it.getValue().second;
+            if (!isRouter) {
+                continue;
+            }
+            final ByteBuffer raResponse = buildRaPacket(it.getValue().first, dstMac, it.getKey());
+            sendResponse(reader, raResponse);
+        }
+    }
+
+    private void replyToNeighborSolicitation(TapPacketReader reader, MacAddress dstMac,
+            Inet6Address dstIp, Inet6Address targetIp) {
+        final Pair<MacAddress, Boolean> neighbor = mNeighborMap.get(targetIp);
+        if (neighbor == null) {
+            return;
+        }
+
+        final MacAddress srcMac = neighbor.first;
+        final boolean isRouter = neighbor.second;
+        int flags = NEIGHBOR_ADVERTISEMENT_FLAG_SOLICITED | NEIGHBOR_ADVERTISEMENT_FLAG_OVERRIDE;
+        if (isRouter) {
+            flags |= NEIGHBOR_ADVERTISEMENT_FLAG_ROUTER;
+        }
+
+        final ByteBuffer tlla = LlaOption.build((byte) ICMPV6_ND_OPTION_TLLA, srcMac);
+        final ByteBuffer naResponse = Ipv6Utils.buildNaPacket(srcMac, dstMac, targetIp, dstIp,
+                flags, targetIp, tlla);
+        sendResponse(reader, naResponse);
+    }
+
     @Override
     protected void replyToPacket(byte[] packet, TapPacketReader reader) {
-        final MacAddress srcMac = MacAddress.fromBytes(
-                Arrays.copyOfRange(packet, ETHER_SRC_ADDR_OFFSET,
-                        ETHER_SRC_ADDR_OFFSET + ETHER_ADDR_LEN));
+        final ByteBuffer buf = ByteBuffer.wrap(packet);
+        // Messages are filtered by parent class, so it is safe to assume that packet is either an
+        // RS or NS.
+        final EthernetHeader ethHdr = Struct.parse(EthernetHeader.class, buf);
+        final Ipv6Header ipv6Hdr = Struct.parse(Ipv6Header.class, buf);
+        final Icmpv6Header icmpv6Header = Struct.parse(Icmpv6Header.class, buf);
 
-        for (Pair<MacAddress, Inet6Address> it : mRouterList) {
-            final ByteBuffer raResponse = buildRaPacket(it.first, srcMac, it.second);
-            try {
-                reader.sendResponse(raResponse);
-            } catch (IOException e) {
-                throw new RuntimeException("Failed to send RA");
-            }
+        if (icmpv6Header.type == ICMPV6_ROUTER_SOLICITATION) {
+            replyToRouterSolicitation(reader, ethHdr.srcMac);
+        } else if (icmpv6Header.type == ICMPV6_NEIGHBOR_SOLICITATION) {
+            final NsHeader nsHeader = Struct.parse(NsHeader.class, buf);
+            replyToNeighborSolicitation(reader, ethHdr.srcMac, ipv6Hdr.srcIp, nsHeader.target);
         }
     }
 }