diff --git a/examples/gcoap/client.c b/examples/gcoap/client.c
index 52b2203489..acf670697a 100644
--- a/examples/gcoap/client.c
+++ b/examples/gcoap/client.c
@@ -174,7 +174,7 @@ static gcoap_socket_type_t _get_tl(const char *uri)
 static ssize_t _send(uint8_t *buf, size_t len, const sock_udp_ep_t *remote,
                      void *ctx, gcoap_socket_type_t tl)
 {
-    ssize_t bytes_sent = gcoap_req_send(buf, len, remote, _resp_handler, ctx, tl);
+    ssize_t bytes_sent = gcoap_req_send(buf, len, remote, NULL, _resp_handler, ctx, tl);
     if (bytes_sent > 0) {
         req_count++;
     }
diff --git a/sys/include/net/gcoap.h b/sys/include/net/gcoap.h
index 4cd99178b9..b9b4afebdd 100644
--- a/sys/include/net/gcoap.h
+++ b/sys/include/net/gcoap.h
@@ -330,7 +330,7 @@
  * coap_opt_add_proxy_uri(&pdu, uri);
  * unsigned len = coap_opt_finish(&pdu, COAP_OPT_FINISH_NONE);
  *
- * gcoap_req_send((uint8_t *) pdu->hdr, len, proxy_remote, _resp_handler, NULL,
+ * gcoap_req_send((uint8_t *) pdu->hdr, len, proxy_remote, NULL, _resp_handler, NULL,
  *                GCOAP_SOCKET_TYPE_UNDEF);
  * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  *
@@ -964,6 +964,7 @@ static inline ssize_t gcoap_request(coap_pkt_t *pdu, uint8_t *buf, size_t len,
  * @param[in] buf           Buffer containing the PDU
  * @param[in] len           Length of the buffer
  * @param[in] remote        Destination for the packet
+ * @param[in] local         Local endpoint to send from, may be NULL
  * @param[in] resp_handler  Callback when response received, may be NULL
  * @param[in] context       User defined context passed to the response handler
  * @param[in] tl_type       The transport type to use for send. When
@@ -980,7 +981,7 @@ static inline ssize_t gcoap_request(coap_pkt_t *pdu, uint8_t *buf, size_t len,
  * @return  0 if cannot send
  */
 ssize_t gcoap_req_send(const uint8_t *buf, size_t len,
-                       const sock_udp_ep_t *remote,
+                       const sock_udp_ep_t *remote, const sock_udp_ep_t *local,
                        gcoap_resp_handler_t resp_handler, void *context,
                        gcoap_socket_type_t tl_type);
 
@@ -1009,7 +1010,7 @@ static inline ssize_t gcoap_req_send_tl(const uint8_t *buf, size_t len,
                                         gcoap_resp_handler_t resp_handler, void *context,
                                         gcoap_socket_type_t tl_type)
 {
-    return gcoap_req_send(buf, len, remote, resp_handler, context, tl_type);
+    return gcoap_req_send(buf, len, remote, NULL, resp_handler, context, tl_type);
 }
 
 /**
diff --git a/sys/include/net/gcoap/forward_proxy.h b/sys/include/net/gcoap/forward_proxy.h
index dc82116322..dc59848d30 100644
--- a/sys/include/net/gcoap/forward_proxy.h
+++ b/sys/include/net/gcoap/forward_proxy.h
@@ -59,6 +59,7 @@ void gcoap_forward_proxy_init(void);
  *
  * @param[in]  pkt           Packet to parse
  * @param[in]  client        Endpoint of the client
+ * @param[in]  local         Local endpoint
  *
  * @return    0              if parsing was successful
  * @return    -ENOTSUP       if the forward proxy is not compiled in
@@ -66,7 +67,7 @@ void gcoap_forward_proxy_init(void);
  * @return    -EINVAL        if Proxy-Uri is malformed
  */
 int gcoap_forward_proxy_request_process(coap_pkt_t *pkt,
-                                        const sock_udp_ep_t *client);
+                                        const sock_udp_ep_t *client, const sock_udp_ep_t *local);
 
 /**
  * @brief  Finds the memo for an outstanding request within the
diff --git a/sys/include/net/nanocoap.h b/sys/include/net/nanocoap.h
index a9cfa2743e..044ea13433 100644
--- a/sys/include/net/nanocoap.h
+++ b/sys/include/net/nanocoap.h
@@ -390,6 +390,16 @@ uint32_t coap_request_ctx_get_tl_type(const coap_request_ctx_t *ctx);
  */
 const sock_udp_ep_t *coap_request_ctx_get_remote_udp(const coap_request_ctx_t *ctx);
 
+/**
+ * @brief   Get the local endpoint on which the request has been received
+ *
+ * @param[in]   ctx The request context
+ *
+ * @return  Local   endpoint to which the request has been received
+ * @return  NULL    The request was not received via UDP
+ */
+const sock_udp_ep_t *coap_request_ctx_get_local_udp(const coap_request_ctx_t *ctx);
+
 /**
  * @brief   Block1 helper struct
  */
diff --git a/sys/net/application_layer/cord/ep/cord_ep.c b/sys/net/application_layer/cord/ep/cord_ep.c
index b9148d9b2b..42e47a77c9 100644
--- a/sys/net/application_layer/cord/ep/cord_ep.c
+++ b/sys/net/application_layer/cord/ep/cord_ep.c
@@ -151,7 +151,8 @@ static int _update_remove(unsigned code, gcoap_resp_handler_t handle)
     ssize_t pkt_len = coap_opt_finish(&pkt, COAP_OPT_FINISH_NONE);
 
     /* send request */
-    ssize_t send_len = gcoap_req_send(buf, pkt_len, &_rd_remote, handle, NULL, GCOAP_SOCKET_TYPE_UNDEF);
+    ssize_t send_len = gcoap_req_send(buf, pkt_len, &_rd_remote, NULL,
+                                      handle, NULL, GCOAP_SOCKET_TYPE_UNDEF);
     if (send_len <= 0) {
         return CORD_EP_ERR;
     }
@@ -225,7 +226,7 @@ static int _discover_internal(const sock_udp_ep_t *remote,
     coap_hdr_set_type(pkt.hdr, COAP_TYPE_CON);
     coap_opt_add_uri_query(&pkt, "rt", "core.rd");
     size_t pkt_len = coap_opt_finish(&pkt, COAP_OPT_FINISH_NONE);
-    res = gcoap_req_send(buf, pkt_len, remote, _on_discover, NULL, GCOAP_SOCKET_TYPE_UNDEF);
+    res = gcoap_req_send(buf, pkt_len, remote, NULL, _on_discover, NULL, GCOAP_SOCKET_TYPE_UNDEF);
     if (res <= 0) {
         return CORD_EP_ERR;
     }
@@ -296,7 +297,7 @@ int cord_ep_register(const sock_udp_ep_t *remote, const char *regif)
     pkt_len += res;
 
     /* send out the request */
-    res = gcoap_req_send(buf, pkt_len, remote, _on_register, NULL, GCOAP_SOCKET_TYPE_UNDEF);
+    res = gcoap_req_send(buf, pkt_len, remote, NULL, _on_register, NULL, GCOAP_SOCKET_TYPE_UNDEF);
     if (res <= 0) {
         retval = CORD_EP_ERR;
         goto end;
diff --git a/sys/net/application_layer/cord/epsim/cord_epsim.c b/sys/net/application_layer/cord/epsim/cord_epsim.c
index 9c739c106f..0f24d4b91a 100644
--- a/sys/net/application_layer/cord/epsim/cord_epsim.c
+++ b/sys/net/application_layer/cord/epsim/cord_epsim.c
@@ -67,7 +67,7 @@ int cord_epsim_register(const sock_udp_ep_t *rd_ep)
     /* finish, we don't have any payload */
     ssize_t len = coap_opt_finish(&pkt, COAP_OPT_FINISH_NONE);
     _state = CORD_EPSIM_BUSY;
-    if (gcoap_req_send(buf, len, rd_ep, _req_handler, NULL, GCOAP_SOCKET_TYPE_UNDEF) == 0) {
+    if (gcoap_req_send(buf, len, rd_ep, NULL, _req_handler, NULL, GCOAP_SOCKET_TYPE_UNDEF) == 0) {
         return CORD_EPSIM_ERROR;
     }
 
diff --git a/sys/net/application_layer/cord/lc/cord_lc.c b/sys/net/application_layer/cord/lc/cord_lc.c
index eddda2f7e7..72d8fd9f0e 100644
--- a/sys/net/application_layer/cord/lc/cord_lc.c
+++ b/sys/net/application_layer/cord/lc/cord_lc.c
@@ -190,7 +190,8 @@ static ssize_t _lookup_raw(const cord_lc_rd_t *rd, unsigned content_format,
     if (pkt_len < 0) {
         return CORD_LC_ERR;
     }
-    res = gcoap_req_send(reqbuf, pkt_len, rd->remote, _on_lookup, NULL, GCOAP_SOCKET_TYPE_UNDEF);
+    res = gcoap_req_send(reqbuf, pkt_len, rd->remote, NULL,
+                         _on_lookup, NULL, GCOAP_SOCKET_TYPE_UNDEF);
     if (res < 0) {
         return CORD_LC_ERR;
     }
@@ -259,7 +260,7 @@ static int _send_rd_init_req(coap_pkt_t *pkt, const sock_udp_ep_t *remote,
         return CORD_LC_ERR;
     }
 
-    if (!gcoap_req_send(buf, pkt_len, remote, _on_rd_init, NULL, GCOAP_SOCKET_TYPE_UNDEF)) {
+    if (!gcoap_req_send(buf, pkt_len, remote, NULL, _on_rd_init, NULL, GCOAP_SOCKET_TYPE_UNDEF)) {
         DEBUG("cord_lc: error gcoap_req_send()\n");
         return CORD_LC_ERR;
     }
diff --git a/sys/net/application_layer/gcoap/dns.c b/sys/net/application_layer/gcoap/dns.c
index 600acf4feb..7273ac1193 100644
--- a/sys/net/application_layer/gcoap/dns.c
+++ b/sys/net/application_layer/gcoap/dns.c
@@ -762,6 +762,6 @@ static ssize_t _send(const void *buf, size_t len, const sock_udp_ep_t *remote,
     if (lock_resp_wait) {
         mutex_lock(&context->resp_wait);
     }
-    return gcoap_req_send(buf, len, remote, _resp_handler, context, tl_type);
+    return gcoap_req_send(buf, len, remote, NULL, _resp_handler, context, tl_type);
 }
 /** @} */
diff --git a/sys/net/application_layer/gcoap/forward_proxy.c b/sys/net/application_layer/gcoap/forward_proxy.c
index ddb95b59c0..550439c77e 100644
--- a/sys/net/application_layer/gcoap/forward_proxy.c
+++ b/sys/net/application_layer/gcoap/forward_proxy.c
@@ -142,8 +142,9 @@ static ssize_t _forward_proxy_handler(coap_pkt_t *pdu, uint8_t *buf,
 {
     int pdu_len;
     const sock_udp_ep_t *remote = coap_request_ctx_get_remote_udp(ctx);
+    const sock_udp_ep_t *local = coap_request_ctx_get_local_udp(ctx);
 
-    pdu_len = gcoap_forward_proxy_request_process(pdu, remote);
+    pdu_len = gcoap_forward_proxy_request_process(pdu, remote, local);
 
     /* Out of memory, reply with 5.00 */
     if (pdu_len == -ENOMEM) {
@@ -226,12 +227,13 @@ static bool _parse_endpoint(sock_udp_ep_t *remote,
     return true;
 }
 
-static ssize_t _dispatch_msg(const void *buf, size_t len, sock_udp_ep_t *remote)
+static ssize_t _dispatch_msg(const void *buf, size_t len, sock_udp_ep_t *remote,
+                             const sock_udp_ep_t *local)
 {
     /* Yes it's not a request -- but turns out there is nothing in
      * gcoap_req_send that is actually request specific, especially if we
      * don't assign a callback. */
-    ssize_t res = gcoap_req_send(buf, len, remote, NULL, NULL,
+    ssize_t res = gcoap_req_send(buf, len, remote, local, NULL, NULL,
                                  GCOAP_SOCKET_TYPE_UDP);
     if (res <= 0) {
         DEBUG("gcoap_forward_proxy: unable to dispatch message: %d\n", -res);
@@ -252,7 +254,7 @@ static void _send_empty_ack(event_t *event)
     /* Flipping byte order as unlike in the other places where mid is
      * used, coap_build_hdr would actually flip it back */
     coap_build_hdr(&buf, COAP_TYPE_ACK, NULL, 0, 0, ntohs(cep->mid));
-    _dispatch_msg(&buf, sizeof(buf), &cep->ep);
+    _dispatch_msg(&buf, sizeof(buf), &cep->ep, &cep->proxy_ep);
 }
 
 static void _set_response_type(coap_pkt_t *pdu, uint8_t resp_type)
@@ -316,7 +318,7 @@ static void _forward_resp_handler(const gcoap_request_memo_t *memo,
     }
     _set_response_type(pdu, _cep_get_response_type(cep));
     /* don't use buf_len here, in case the above `gcoap_resp_init`s changed `pdu` */
-    _dispatch_msg(pdu->hdr, coap_get_total_len(pdu), &cep->ep);
+    _dispatch_msg(pdu->hdr, coap_get_total_len(pdu), &cep->ep, &cep->proxy_ep);
     _free_client_ep(cep);
 }
 
@@ -398,6 +400,7 @@ static int _gcoap_forward_proxy_copy_options(coap_pkt_t *pkt,
 
     /* copy payload from client_pkt to pkt */
     memcpy(pkt->payload, client_pkt->payload, client_pkt->payload_len);
+    pkt->payload_len = client_pkt->payload_len;
     len += client_pkt->payload_len;
 
     return len;
@@ -407,7 +410,7 @@ int gcoap_forward_proxy_req_send(client_ep_t *cep)
 {
     int len;
     if ((len = gcoap_req_send((uint8_t *)cep->pdu.hdr, coap_get_total_len(&cep->pdu),
-                             &cep->server_ep, _forward_resp_handler, cep,
+                             &cep->server_ep, NULL, _forward_resp_handler, cep,
                              GCOAP_SOCKET_TYPE_UNDEF)) <= 0) {
         DEBUG("gcoap_forward_proxy_req_send(): gcoap_req_send failed %d\n", len);
         _free_client_ep(cep);
@@ -458,7 +461,7 @@ static int _gcoap_forward_proxy_via_coap(coap_pkt_t *client_pkt,
     /* copy all options from client_pkt to pkt */
     len = _gcoap_forward_proxy_copy_options(&client_ep->pdu, client_pkt, client_ep, urip);
 
-    if (len == -EINVAL) {
+    if (len < 0) {
         _free_client_ep(client_ep);
         return -EINVAL;
     }
@@ -479,13 +482,13 @@ static int _gcoap_forward_proxy_via_coap(coap_pkt_t *client_pkt,
 }
 
 int gcoap_forward_proxy_request_process(coap_pkt_t *pkt,
-                                        const sock_udp_ep_t *client) {
+                                        const sock_udp_ep_t *client, const sock_udp_ep_t *local) {
     char *uri;
     uri_parser_result_t urip;
     ssize_t optlen = 0;
 
     client_ep_t *cep = _allocate_client_ep(client);
-
+    cep->proxy_ep = local ? *local : (sock_udp_ep_t){ 0 };
     if (!cep) {
         return -ENOMEM;
     }
diff --git a/sys/net/application_layer/gcoap/gcoap.c b/sys/net/application_layer/gcoap/gcoap.c
index e6fc5d91ff..3c7da0da84 100644
--- a/sys/net/application_layer/gcoap/gcoap.c
+++ b/sys/net/application_layer/gcoap/gcoap.c
@@ -66,7 +66,7 @@ static ssize_t _well_known_core_handler(coap_pkt_t* pdu, uint8_t *buf, size_t le
                                         coap_request_ctx_t *ctx);
 static void _cease_retransmission(gcoap_request_memo_t *memo);
 static size_t _handle_req(gcoap_socket_t *sock, coap_pkt_t *pdu, uint8_t *buf,
-                          size_t len, sock_udp_ep_t *remote);
+                          size_t len, sock_udp_ep_t *remote, sock_udp_aux_tx_t *aux);
 static void _expire_request(gcoap_request_memo_t *memo);
 static gcoap_request_memo_t* _find_req_memo_by_mid(const sock_udp_ep_t *remote,
                                                    uint16_t mid);
@@ -453,7 +453,7 @@ static void _process_coap_pdu(gcoap_socket_t *sock, sock_udp_ep_t *remote, sock_
                                          COAP_CODE_REQUEST_ENTITY_TOO_LARGE);
             } else {
                 pdu_len = _handle_req(sock, &pdu, _listen_buf,
-                                      sizeof(_listen_buf), remote);
+                                      sizeof(_listen_buf), remote, aux);
             }
 
             if (pdu_len > 0) {
@@ -652,7 +652,7 @@ static void _cease_retransmission(gcoap_request_memo_t *memo) {
  * return length of response pdu, or < 0 if can't handle
  */
 static size_t _handle_req(gcoap_socket_t *sock, coap_pkt_t *pdu, uint8_t *buf,
-                          size_t len, sock_udp_ep_t *remote)
+                          size_t len, sock_udp_ep_t *remote, sock_udp_aux_tx_t *aux)
 {
     const coap_resource_t *resource     = NULL;
     gcoap_listener_t *listener          = NULL;
@@ -760,6 +760,7 @@ static size_t _handle_req(gcoap_socket_t *sock, coap_pkt_t *pdu, uint8_t *buf,
         .resource = resource,
         .tl_type = (uint32_t)sock->type,
         .remote = remote,
+        .local = aux ? &aux->local : NULL,
     };
 
     pdu_len = resource->handler(pdu, buf, len, &ctx);
@@ -1613,7 +1614,7 @@ int gcoap_obs_req_forget(const sock_udp_ep_t *remote, const uint8_t *token,
 }
 
 ssize_t gcoap_req_send(const uint8_t *buf, size_t len,
-                       const sock_udp_ep_t *remote,
+                       const sock_udp_ep_t *remote, const sock_udp_ep_t *local,
                        gcoap_resp_handler_t resp_handler, void *context,
                        gcoap_socket_type_t tl_type)
 {
@@ -1743,7 +1744,12 @@ ssize_t gcoap_req_send(const uint8_t *buf, size_t len,
     }
 
     if (res == 0) {
-        res = _tl_send(&socket, buf, len, remote, NULL);
+        sock_udp_aux_tx_t aux = { 0 };
+        if (local) {
+            memcpy(&aux.local, local, sizeof(sock_udp_ep_t));
+            aux.flags = SOCK_AUX_SET_LOCAL;
+        }
+        res = _tl_send(&socket, buf, len, remote, &aux);
     }
     if (res <= 0) {
         if (memo != NULL) {
diff --git a/sys/net/application_layer/gcoap/include/forward_proxy_internal.h b/sys/net/application_layer/gcoap/include/forward_proxy_internal.h
index dbeb93fbf5..8831c19d88 100644
--- a/sys/net/application_layer/gcoap/include/forward_proxy_internal.h
+++ b/sys/net/application_layer/gcoap/include/forward_proxy_internal.h
@@ -40,6 +40,7 @@ typedef struct {
     coap_pkt_t pdu;                         /**< forward CoAP PDU */
     sock_udp_ep_t server_ep;                /**< forward Server endpoint */
     sock_udp_ep_t ep;                       /**< client endpoint */
+    sock_udp_ep_t proxy_ep;                 /**< proxy endpoint */
     uint16_t mid;                           /**< message ID */
     uint8_t flags;                          /**< client flags */
 #if IS_USED(MODULE_NANOCOAP_CACHE)
diff --git a/sys/net/application_layer/nanocoap/nanocoap.c b/sys/net/application_layer/nanocoap/nanocoap.c
index f7e92cc3fd..08af915cd0 100644
--- a/sys/net/application_layer/nanocoap/nanocoap.c
+++ b/sys/net/application_layer/nanocoap/nanocoap.c
@@ -1464,3 +1464,13 @@ const sock_udp_ep_t *coap_request_ctx_get_remote_udp(const coap_request_ctx_t *c
 {
     return ctx->remote;
 }
+
+const sock_udp_ep_t *coap_request_ctx_get_local_udp(const coap_request_ctx_t *ctx)
+{
+#if defined(MODULE_SOCK_AUX_LOCAL)
+    return ctx->local;
+#else
+    (void)ctx;
+    return NULL;
+#endif
+}