diff --git a/src/ipv6_assist/ipv6_assist_server.erl b/src/ipv6_assist/ipv6_assist_server.erl
index 506b2d5..c9e0b5f 100644
--- a/src/ipv6_assist/ipv6_assist_server.erl
+++ b/src/ipv6_assist/ipv6_assist_server.erl
@@ -84,13 +84,13 @@ handle_info({udp, Sock, Ip, Port, Body}, State = #state{socket = Sock}) ->
         #'SDLV6AssistProbe'{assist_token = Token} ->
             case sdlan_token_store:lookup(Token) of
                 true ->
-                    Reply = sdlan_pb:encode_msg(#'SDLV6AssistProbeReply'{
-                        v6_info = #'SDLV6Info' {
-                            v6 = Ip,
-                            port = Port
-                        }
-                    }),
-                    ok = gen_udp:send(Sock, Ip, Port, Reply);
+                    case ipv6_assist_probe_reply(Ip, Port) of
+                        Reply = #'SDLV6AssistProbeReply'{} ->
+                            ReplyBin = sdlan_pb:encode_msg(Reply),
+                            ok = gen_udp:send(Sock, Ip, Port, ReplyBin);
+                        undefined ->
+                            ok
+                    end;
                 false ->
                     ok
             end;
@@ -111,3 +111,20 @@ terminate(_Reason, _State = #state{}) ->
     {ok, NewState :: #state{}} | {error, Reason :: term()}.
 code_change(_OldVsn, State = #state{}, _Extra) ->
     {ok, State}.
+
+-spec ipv6_assist_probe_reply(Ip :: inet:ip_address(), Port :: integer()) ->
+    undefined | #'SDLV6AssistProbeReply'{}.
+ipv6_assist_probe_reply(Ip, Port) when is_integer(Port), Port > 0, Port =< 65535 ->
+    case sdlan_util:ipv6_to_bytes(Ip) of
+        <<_:128>> = V6Bytes ->
+            #'SDLV6AssistProbeReply'{
+                v6_info = #'SDLV6Info'{
+                    v6 = V6Bytes,
+                    port = Port
+                }
+            };
+        _ ->
+            undefined
+    end;
+ipv6_assist_probe_reply(_, _) ->
+    undefined.
\ No newline at end of file