diff --git a/src/ipc.proto b/src/ipc.proto
index f2498bca..b5242872 100644
--- a/src/ipc.proto
+++ b/src/ipc.proto
@@ -48,6 +48,8 @@ message auth_reply_msg
 	repeated string nbns = 23;
 	optional bool no_udp = 24 [default = false];
 	optional string xml_config_file = 26;
+	optional string ipv4_network = 27;
+	optional string ipv6_network = 28;
 }
 
 /* RESUME_FETCH_REQ + RESUME_DELETE_REQ */
diff --git a/src/main-auth.c b/src/main-auth.c
index 9d2a9856..5bda1c26 100644
--- a/src/main-auth.c
+++ b/src/main-auth.c
@@ -85,6 +85,10 @@ int send_cookie_auth_reply(main_server_st* s, struct proc_st* proc,
 
 		msg.ipv4_netmask = proc->config.ipv4_netmask;
 		msg.ipv6_netmask = proc->config.ipv6_netmask;
+
+		msg.ipv4_network = proc->config.ipv4_network;
+		msg.ipv6_network = proc->config.ipv6_network;
+
 		msg.ipv6_prefix = proc->config.ipv6_prefix;
 		if (proc->config.rx_per_sec != 0) {
 			msg.has_rx_per_sec = 1;
diff --git a/src/vpn.h b/src/vpn.h
index 593341a5..d5446df6 100644
--- a/src/vpn.h
+++ b/src/vpn.h
@@ -156,9 +156,11 @@ struct group_cfg_st {
 struct vpn_st {
 	char name[IFNAMSIZ];
 	char *ipv4_netmask;
+	char *ipv4_network;
 	char *ipv4;
 	char *ipv4_local; /* local IPv4 address */
 	char *ipv6_netmask;
+	char *ipv6_network;
 	unsigned ipv6_prefix;
 
 	char *ipv6;
diff --git a/src/worker-auth.c b/src/worker-auth.c
index dca9e867..4cbc667f 100644
--- a/src/worker-auth.c
+++ b/src/worker-auth.c
@@ -554,6 +554,18 @@ static int recv_cookie_auth_reply(worker_st * ws)
 				    talloc_strdup(ws, msg->ipv6_netmask);
 			}
 
+			if (msg->ipv4_network != NULL) {
+				talloc_free(ws->config->network.ipv4_network);
+				ws->config->network.ipv4_network =
+				    talloc_strdup(ws, msg->ipv4_network);
+			}
+
+			if (msg->ipv6_network != NULL) {
+				talloc_free(ws->config->network.ipv6_network);
+				ws->config->network.ipv6_network =
+				    talloc_strdup(ws, msg->ipv6_network);
+			}
+
 			ws->config->network.ipv6_prefix = msg->ipv6_prefix;
 
 			if (msg->has_rx_per_sec)
diff --git a/src/worker-misc.c b/src/worker-misc.c
index bde24d7d..db16f4cf 100644
--- a/src/worker-misc.c
+++ b/src/worker-misc.c
@@ -224,6 +224,9 @@ int complete_vpn_info(worker_st * ws, struct vpn_st *vinfo)
 	if (check_if_default_route(vinfo->routes, vinfo->routes_size))
 		ws->default_route = 1;
 
+	vinfo->ipv4_network = ws->config->network.ipv4_network;
+	vinfo->ipv6_network = ws->config->network.ipv6_network;
+
 	vinfo->ipv4_netmask = ws->config->network.ipv4_netmask;
 	vinfo->ipv6_netmask = ws->config->network.ipv6_netmask;
 	vinfo->ipv6_prefix = ws->config->network.ipv6_prefix;
diff --git a/src/worker-vpn.c b/src/worker-vpn.c
index e5a95ac5..a842976c 100644
--- a/src/worker-vpn.c
+++ b/src/worker-vpn.c
@@ -1514,14 +1514,14 @@ static int connect_handler(worker_st * ws)
 			    tls_printf(ws->session, "X-CSTP-Address: %s\r\n",
 				       ws->vinfo.ipv6);
 			SEND_ERR(ret);
+		}
 
-			if (ws->vinfo.ipv6_netmask) {
-				ret =
-				    tls_printf(ws->session,
-					       "X-CSTP-Netmask: %u\r\n",
-					       ws->vinfo.ipv6_prefix);
-				SEND_ERR(ret);
-			}
+		if (ws->vinfo.ipv6_network && ws->vinfo.ipv6_prefix != 0) {
+			ret =
+			    tls_printf(ws->session,
+				       "X-CSTP-Netmask: %s/%u\r\n",
+					       ws->vinfo.ipv6_network, ws->vinfo.ipv6_prefix);
+			SEND_ERR(ret);
 		}
 	}