diff --git a/README.md b/README.md
index 6902bdf..0f58790 100644
--- a/README.md
+++ b/README.md
@@ -43,9 +43,10 @@ docker run -d --network=host -e MTP_PORT=443 -e MTP_SECRET=d0d6e111bada5511fcce9
 
 Where
 
-* `-p 443` / `MTP_PORT` proxy port
-* `-s d0d6e111bada5511fcce9584deadbeef` / `MTP_SECRET` proxy secret (don't append `dd`! it should be 32 chars long!)
-* `-t dcbe8f1493fa4cd9ab300891c0b5b326` / `MTP_TAG` ad-tag that you get from [@MTProxybot](https://t.me/MTProxybot)
+* `-p 443` / `MTP_PORT=…` proxy port
+* `-s d0d6e111bada5511fcce9584deadbeef` / `MTP_SECRET=…` proxy secret (don't append `dd`! it should be 32 chars long!)
+* `-t dcbe8f1493fa4cd9ab300891c0b5b326` / `MTP_TAG=…` ad-tag that you get from [@MTProxybot](https://t.me/MTProxybot)
+* `-d` / `MTP_DD_ONLY=t` only allow "secure" connections (dd-secrets)
 
 ### To run with custom config-file
 
@@ -274,6 +275,6 @@ Helpers
 
 Number of connections
 
-```erlang
+```bash
 /opt/mtp_proxy/bin/mtp_proxy eval 'lists:sum([proplists:get_value(all_connections, L) || {_, L} <- ranch:info()]).'
 ```
diff --git a/src/mtproto_proxy.app.src b/src/mtproto_proxy.app.src
index e850945..d45d44f 100644
--- a/src/mtproto_proxy.app.src
+++ b/src/mtproto_proxy.app.src
@@ -30,7 +30,7 @@
         %% `ip_lookup_services' will be tried one-by-one: if 1st is not responding,
         %% 2nd one will be tried and so on
         {ip_lookup_services,
-         ["http://ip.seriyps.ru/",
+         ["http://ipv4.seriyps.ru/",
           "https://digitalresistance.dog/myIp",
           "http://ipv4.myexternalip.com/raw"]},
         %% {external_ip, "YOUR.SERVER.EXTERNAL.IP"},
diff --git a/start.sh b/start.sh
index b755948..5ead358 100755
--- a/start.sh
+++ b/start.sh
@@ -2,6 +2,7 @@
 # Script that helps to overwrite port/secret/ad tag from command line without changing config-files
 
 CMD="/opt/mtp_proxy/bin/mtp_proxy foreground"
+# CMD="/opt/mtp_proxy/bin/mtp_proxy console"
 THIS=$0
 
 usage() {
@@ -10,13 +11,16 @@ usage() {
     echo "${THIS}"
     echo "To start in single-port mode configured from command-line:"
     echo "${THIS} -p <port> -s <secret> -t <ad tag>"
+    echo "To only allow connections with randomized protocol (dd-secrets):"
+    echo "${THIS} -d"
     echo "Parameters:"
     echo "-p <port>: port to listen on. 1-65535"
     echo "-s <secret>: proxy secret. 32 hex characters 0-9 a-f"
-    echo "-t <ad tag>: promo tag, that you get from @MTProxybot. 32 hex characters"
-    echo "port secret and tag can also be configured via environment variables:"
-    echo "MTP_PORT, MTP_SECRET, MTP_TAG"
-    echo "If both command line and environment are set, command line have higher priority"
+    echo "-t <ad tag>: promo tag that you get from @MTProxybot. 32 hex characters"
+    echo "-d: only allow 'secure' connections (with dd-secret)"
+    echo "port, secret, tag and secure mode can also be configured via environment variables:"
+    echo "MTP_PORT, MTP_SECRET, MTP_TAG, MTP_DD_ONLY"
+    echo "If both command line and environment are set, command line have higher priority."
 }
 
 error() {
@@ -29,9 +33,10 @@ error() {
 PORT=${MTP_PORT:-""}
 SECRET=${MTP_SECRET:-""}
 TAG=${MTP_TAG:-""}
+DD_ONLY=${MTP_DD_ONLY:-""}
 
 # check command line options
-while getopts "p:s:t:h" o; do
+while getopts "p:s:t:dh" o; do
     case "${o}" in
         p)
             PORT=${OPTARG}
@@ -42,16 +47,25 @@ while getopts "p:s:t:h" o; do
         t)
             TAG=${OPTARG}
             ;;
+        d)
+            DD_ONLY="y"
+            ;;
         h)
             usage
             exit 0
     esac
 done
 
+DD_ARG=""
+
+if [ -n "${DD_ONLY}" ]; then
+    DD_ARG='-mtproto_proxy allowed_protocols [mtp_secure]'
+fi
+
 # if at least one option is set...
 if [ -n "${PORT}" -o -n "${SECRET}" -o -n "${TAG}" ]; then
     # If at least one of them not set...
-    [ -z "${PORT}" -o -z "${SECRET}" -o -z "${SECRET}" ] && \
+    [ -z "${PORT}" -o -z "${SECRET}" -o -z "${TAG}" ] && \
         error "Not enough options: -p '${PORT}' -s '${SECRET}' -t '${TAG}'"
 
     # validate format
@@ -62,7 +76,7 @@ if [ -n "${PORT}" -o -n "${SECRET}" -o -n "${TAG}" ]; then
     [ -n "`echo $TAG | grep -x '[[:xdigit:]]\{32\}'`" ] || \
         error "Invalid tag. Should be 32 chars of 0-9 a-f"
 
-    exec $CMD -mtproto_proxy ports "[#{name => mtproto_proxy, port => $PORT, secret => <<\"$SECRET\">>, tag => <<\"$TAG\">>}]"
+    exec $CMD $DD_ARG -mtproto_proxy ports "[#{name => mtproto_proxy, port => $PORT, secret => <<\"$SECRET\">>, tag => <<\"$TAG\">>}]"
 else
-    exec $CMD
+    exec $CMD $DD_ARG
 fi