diff --git a/src/transport_layer/etcp_connections.c b/src/transport_layer/etcp_connections.c
index ca32a76d..deec78ca 100644
--- a/src/transport_layer/etcp_connections.c
+++ b/src/transport_layer/etcp_connections.c
@@ -1797,6 +1797,10 @@ static int handle_ping(struct ETCP_SOCKET* e_sock, struct ETCP_DGRAM* pkt, const
     if ((flags & ETCP_PING_FLAG_OBSERVE) && (flags & ETCP_PING_FLAG_ADDRESS_CHECK)) {
         DEBUG_WARN(DEBUG_CATEGORY_NAT, "UDP probe has incompatible flags=%02x", flags); return 7;
     }
+    if ((flags & ETCP_PING_FLAG_NO_REPLY) &&
+        (!(flags & (ETCP_PING_FLAG_OBSERVE | ETCP_PING_FLAG_ADDRESS_CHECK)) || ulen != ROUTE_OBSERVE_TAG_SIZE + 9)) {
+        DEBUG_WARN(DEBUG_CATEGORY_NAT, "One-way NAT probe has invalid flags=%02x tag_size=%u", flags, ulen); return 7;
+    }
     if (!nat_detection_ping_allowed(e_sock->instance->nat_det, e_sock, decrypted_pubkey, addr, flags, udata, ulen)) {
         memory_pool_free(e_sock->instance->pkt_pool, pkt); return 0;
     }
@@ -1806,6 +1810,10 @@ static int handle_ping(struct ETCP_SOCKET* e_sock, struct ETCP_DGRAM* pkt, const
     if ((flags & ETCP_PING_FLAG_ADDRESS_CHECK) && e_sock->instance->nat_det)
         nat_detection_receive_ingress(e_sock->instance->nat_det, e_sock, decrypted_pubkey, addr, udata, ulen);
 
+    if (flags & ETCP_PING_FLAG_NO_REPLY) {
+        memory_pool_free(e_sock->instance->pkt_pool, pkt); return 0;
+    }
+
     if ((flags & ETCP_PING_FLAG_SEND_RTT) && ulen >= 2) {
         uint16_t rtt_val = wire_read16(udata);
         topo_node_ping_update_rtt(e_sock->instance->topo_groups, peer_id, rtt_val);
diff --git a/src/transport_layer/etcp_connections.h b/src/transport_layer/etcp_connections.h
index e5005d0f..04f5a248 100644
--- a/src/transport_layer/etcp_connections.h
+++ b/src/transport_layer/etcp_connections.h
@@ -49,6 +49,7 @@ extern "C" {
 #define ETCP_PING_FLAG_SEND_RTT 0x02  // в PING: несу RTT для получателя
 #define ETCP_PING_FLAG_OBSERVE 0x04   // PONG несёт фактически наблюдаемый IP:port
 #define ETCP_PING_FLAG_ADDRESS_CHECK 0x08 // прямое входящее испытание endpoint
+#define ETCP_PING_FLAG_NO_REPLY 0x10 // NAT-проба: результат через router, без автоматического UDP-ответа
 
 /* Адаптивный keepalive */
 #define KA_PERIOD_MIN_MS   200