diff --git a/extras/vpnupgrade.sh b/extras/vpnupgrade.sh
index c760db0..0bee9df 100755
--- a/extras/vpnupgrade.sh
+++ b/extras/vpnupgrade.sh
@@ -15,7 +15,7 @@
 # know how you have improved it!
 
 # (Optional) Specify which Libreswan version to install. See: https://libreswan.org
-# NOTE: If not specified, the latest supported version will be installed.
+# If not specified, the latest supported version will be installed.
 SWAN_VER=
 
 ### DO NOT edit below this line ###
diff --git a/extras/vpnupgrade_alpine.sh b/extras/vpnupgrade_alpine.sh
index c86ae08..94ef0d4 100755
--- a/extras/vpnupgrade_alpine.sh
+++ b/extras/vpnupgrade_alpine.sh
@@ -13,8 +13,9 @@
 # Attribution required: please include my name in any derivative and let me
 # know how you have improved it!
 
-# Specify which Libreswan version to install. See: https://libreswan.org
-SWAN_VER=4.6
+# (Optional) Specify which Libreswan version to install. See: https://libreswan.org
+# If not specified, the latest supported version will be installed.
+SWAN_VER=
 
 ### DO NOT edit below this line ###
 
@@ -55,20 +56,6 @@ check_os() {
 }
 
 check_libreswan() {
-  case $SWAN_VER in
-    4.[5-6])
-      true
-      ;;
-    *)
-cat 1>&2 <<EOF
-Error: Libreswan version '$SWAN_VER' is not supported.
-       This script can install one of these versions:
-       4.5 or 4.6
-EOF
-      exit 1
-      ;;
-  esac
-
   ipsec_ver=$(/usr/local/sbin/ipsec --version 2>/dev/null)
   swan_ver_old=$(printf '%s' "$ipsec_ver" | sed -e 's/.*Libreswan U\?//' -e 's/\( (\|\/K\).*//')
   if ! printf '%s' "$ipsec_ver" | grep -q "Libreswan"; then
@@ -80,6 +67,29 @@ EOF
   fi
 }
 
+get_swan_ver() {
+  swan_ver_cur=4.6
+  base_url="https://github.com/hwdsl2/vpn-extras/releases/download/v1.0.0"
+  swan_ver_url="$base_url/upg-v1-$os_type-$os_ver-swanver"
+  swan_ver_latest=$(wget -t 3 -T 15 -qO- "$swan_ver_url" | head -n 1)
+  if printf '%s' "$swan_ver_latest" | grep -Eq '^([3-9]|[1-9][0-9]{1,2})(\.([0-9]|[1-9][0-9]{1,2})){1,2}$'; then
+    swan_ver_cur="$swan_ver_latest"
+  fi
+  [ -z "$SWAN_VER" ] && SWAN_VER="$swan_ver_cur"
+}
+
+check_swan_ver() {
+  if ! printf '%s\n%s' "4.5" "$SWAN_VER" | sort -C -V \
+    || ! printf '%s\n%s' "$SWAN_VER" "$swan_ver_cur" | sort -C -V; then
+cat 1>&2 <<EOF
+Error: Libreswan version '$SWAN_VER' is not supported.
+       This script can install one of these versions:
+       4.5-$swan_ver_cur
+EOF
+    exit 1
+  fi
+}
+
 show_setup_info() {
 cat <<EOF
 
@@ -96,7 +106,7 @@ Note: This script will make the following changes to your VPN configuration:
 
 EOF
 
-  if [ "$SWAN_VER" != "4.6" ]; then
+  if [ "$SWAN_VER" != "$swan_ver_cur" ]; then
 cat <<'EOF'
 WARNING: Older versions of Libreswan could contain known security vulnerabilities.
          See https://libreswan.org/security/ for more information.
@@ -262,10 +272,8 @@ IMPORTANT: You must edit /etc/ipsec.conf and replace
            all occurrences of these two lines:
              modecfgdns1=DNS_SERVER_1
              modecfgdns2=DNS_SERVER_2
-
            with a single line like this:
              modecfgdns="DNS_SERVER_1 DNS_SERVER_2"
-
            Then run "sudo service ipsec restart".
 
 EOF
@@ -277,6 +285,8 @@ vpnupgrade() {
   check_vz
   check_os
   check_libreswan
+  get_swan_ver
+  check_swan_ver
   show_setup_info
   start_setup
   install_pkgs
diff --git a/extras/vpnupgrade_amzn.sh b/extras/vpnupgrade_amzn.sh
index 175698f..7c14282 100755
--- a/extras/vpnupgrade_amzn.sh
+++ b/extras/vpnupgrade_amzn.sh
@@ -13,8 +13,9 @@
 # Attribution required: please include my name in any derivative and let me
 # know how you have improved it!
 
-# Specify which Libreswan version to install. See: https://libreswan.org
-SWAN_VER=4.6
+# (Optional) Specify which Libreswan version to install. See: https://libreswan.org
+# If not specified, the latest supported version will be installed.
+SWAN_VER=
 
 ### DO NOT edit below this line ###
 
@@ -38,20 +39,6 @@ check_os() {
 }
 
 check_libreswan() {
-  case $SWAN_VER in
-    3.32|4.[1-6])
-      true
-      ;;
-    *)
-cat 1>&2 <<EOF
-Error: Libreswan version '$SWAN_VER' is not supported.
-       This script can install one of these versions:
-       3.32, 4.1-4.6
-EOF
-      exit 1
-      ;;
-  esac
-
   ipsec_ver=$(/usr/local/sbin/ipsec --version 2>/dev/null)
   swan_ver_old=$(printf '%s' "$ipsec_ver" | sed -e 's/.*Libreswan U\?//' -e 's/\( (\|\/K\).*//')
   if ! printf '%s' "$ipsec_ver" | grep -q "Libreswan"; then
@@ -63,6 +50,30 @@ EOF
   fi
 }
 
+get_swan_ver() {
+  swan_ver_cur=4.6
+  base_url="https://github.com/hwdsl2/vpn-extras/releases/download/v1.0.0"
+  swan_ver_url="$base_url/upg-v1-amzn-2-swanver"
+  swan_ver_latest=$(wget -t 3 -T 15 -qO- "$swan_ver_url" | head -n 1)
+  if printf '%s' "$swan_ver_latest" | grep -Eq '^([3-9]|[1-9][0-9]{1,2})(\.([0-9]|[1-9][0-9]{1,2})){1,2}$'; then
+    swan_ver_cur="$swan_ver_latest"
+  fi
+  [ -z "$SWAN_VER" ] && SWAN_VER="$swan_ver_cur"
+}
+
+check_swan_ver() {
+  if [ "$SWAN_VER" != "3.32" ] \
+    && { ! printf '%s\n%s' "4.1" "$SWAN_VER" | sort -C -V \
+    || ! printf '%s\n%s' "$SWAN_VER" "$swan_ver_cur" | sort -C -V; }; then
+cat 1>&2 <<EOF
+Error: Libreswan version '$SWAN_VER' is not supported.
+       This script can install one of these versions:
+       3.32, 4.1-$swan_ver_cur
+EOF
+    exit 1
+  fi
+}
+
 show_setup_info() {
 cat <<EOF
 
@@ -79,7 +90,7 @@ Note: This script will make the following changes to your VPN configuration:
 
 EOF
 
-  if [ "$SWAN_VER" != "4.6" ]; then
+  if [ "$SWAN_VER" != "$swan_ver_cur" ]; then
 cat <<'EOF'
 WARNING: Older versions of Libreswan could contain known security vulnerabilities.
          See https://libreswan.org/security/ for more information.
@@ -250,10 +261,8 @@ IMPORTANT: You must edit /etc/ipsec.conf and replace
            all occurrences of these two lines:
              modecfgdns1=DNS_SERVER_1
              modecfgdns2=DNS_SERVER_2
-
            with a single line like this:
              modecfgdns="DNS_SERVER_1 DNS_SERVER_2"
-
            Then run "sudo service ipsec restart".
 
 EOF
@@ -264,6 +273,8 @@ vpnupgrade() {
   check_root
   check_os
   check_libreswan
+  get_swan_ver
+  check_swan_ver
   show_setup_info
   start_setup
   install_pkgs
diff --git a/extras/vpnupgrade_centos.sh b/extras/vpnupgrade_centos.sh
index cb336f6..eb1eda3 100755
--- a/extras/vpnupgrade_centos.sh
+++ b/extras/vpnupgrade_centos.sh
@@ -13,8 +13,9 @@
 # Attribution required: please include my name in any derivative and let me
 # know how you have improved it!
 
-# Specify which Libreswan version to install. See: https://libreswan.org
-SWAN_VER=4.6
+# (Optional) Specify which Libreswan version to install. See: https://libreswan.org
+# If not specified, the latest supported version will be installed.
+SWAN_VER=
 
 ### DO NOT edit below this line ###
 
@@ -56,20 +57,6 @@ check_os() {
 }
 
 check_libreswan() {
-  case $SWAN_VER in
-    3.32|4.[1-6])
-      true
-      ;;
-    *)
-cat 1>&2 <<EOF
-Error: Libreswan version '$SWAN_VER' is not supported.
-       This script can install one of these versions:
-       3.32, 4.1-4.6
-EOF
-      exit 1
-      ;;
-  esac
-
   ipsec_ver=$(/usr/local/sbin/ipsec --version 2>/dev/null)
   swan_ver_old=$(printf '%s' "$ipsec_ver" | sed -e 's/.*Libreswan U\?//' -e 's/\( (\|\/K\).*//')
   if ! printf '%s' "$ipsec_ver" | grep -q "Libreswan"; then
@@ -81,6 +68,30 @@ EOF
   fi
 }
 
+get_swan_ver() {
+  swan_ver_cur=4.6
+  base_url="https://github.com/hwdsl2/vpn-extras/releases/download/v1.0.0"
+  swan_ver_url="$base_url/upg-v1-$os_type-$os_ver-swanver"
+  swan_ver_latest=$(wget -t 3 -T 15 -qO- "$swan_ver_url" | head -n 1)
+  if printf '%s' "$swan_ver_latest" | grep -Eq '^([3-9]|[1-9][0-9]{1,2})(\.([0-9]|[1-9][0-9]{1,2})){1,2}$'; then
+    swan_ver_cur="$swan_ver_latest"
+  fi
+  [ -z "$SWAN_VER" ] && SWAN_VER="$swan_ver_cur"
+}
+
+check_swan_ver() {
+  if [ "$SWAN_VER" != "3.32" ] \
+    && { ! printf '%s\n%s' "4.1" "$SWAN_VER" | sort -C -V \
+    || ! printf '%s\n%s' "$SWAN_VER" "$swan_ver_cur" | sort -C -V; }; then
+cat 1>&2 <<EOF
+Error: Libreswan version '$SWAN_VER' is not supported.
+       This script can install one of these versions:
+       3.32, 4.1-$swan_ver_cur
+EOF
+    exit 1
+  fi
+}
+
 show_setup_info() {
 cat <<EOF
 
@@ -97,7 +108,7 @@ Note: This script will make the following changes to your VPN configuration:
 
 EOF
 
-  if [ "$SWAN_VER" != "4.6" ]; then
+  if [ "$SWAN_VER" != "$swan_ver_cur" ]; then
 cat <<'EOF'
 WARNING: Older versions of Libreswan could contain known security vulnerabilities.
          See https://libreswan.org/security/ for more information.
@@ -286,10 +297,8 @@ IMPORTANT: You must edit /etc/ipsec.conf and replace
            all occurrences of these two lines:
              modecfgdns1=DNS_SERVER_1
              modecfgdns2=DNS_SERVER_2
-
            with a single line like this:
              modecfgdns="DNS_SERVER_1 DNS_SERVER_2"
-
            Then run "sudo service ipsec restart".
 
 EOF
@@ -301,6 +310,8 @@ vpnupgrade() {
   check_vz
   check_os
   check_libreswan
+  get_swan_ver
+  check_swan_ver
   show_setup_info
   start_setup
   install_pkgs_1
diff --git a/extras/vpnupgrade_ubuntu.sh b/extras/vpnupgrade_ubuntu.sh
index c82a510..dbd9188 100755
--- a/extras/vpnupgrade_ubuntu.sh
+++ b/extras/vpnupgrade_ubuntu.sh
@@ -13,8 +13,9 @@
 # Attribution required: please include my name in any derivative and let me
 # know how you have improved it!
 
-# Specify which Libreswan version to install. See: https://libreswan.org
-SWAN_VER=4.6
+# (Optional) Specify which Libreswan version to install. See: https://libreswan.org
+# If not specified, the latest supported version will be installed.
+SWAN_VER=
 
 ### DO NOT edit below this line ###
 
@@ -61,24 +62,6 @@ check_os() {
 }
 
 check_libreswan() {
-  case $SWAN_VER in
-    3.32|4.[1-6])
-      true
-      ;;
-    *)
-cat 1>&2 <<EOF
-Error: Libreswan version '$SWAN_VER' is not supported.
-       This script can install one of these versions:
-       3.32, 4.1-4.6
-EOF
-      exit 1
-      ;;
-  esac
-
-if [ "$SWAN_VER" = "3.32" ] && [ "$os_ver" = "11" ]; then
-  exiterr "Libreswan 3.32 is not supported on Debian 11."
-fi
-
   ipsec_ver=$(/usr/local/sbin/ipsec --version 2>/dev/null)
   swan_ver_old=$(printf '%s' "$ipsec_ver" | sed -e 's/.*Libreswan U\?//' -e 's/\( (\|\/K\).*//')
   if ! printf '%s' "$ipsec_ver" | grep -q "Libreswan"; then
@@ -90,6 +73,34 @@ EOF
   fi
 }
 
+get_swan_ver() {
+  swan_ver_cur=4.6
+  base_url="https://github.com/hwdsl2/vpn-extras/releases/download/v1.0.0"
+  swan_ver_url="$base_url/upg-v1-$os_type-$os_ver-swanver"
+  swan_ver_latest=$(wget -t 3 -T 15 -qO- "$swan_ver_url" | head -n 1)
+  if printf '%s' "$swan_ver_latest" | grep -Eq '^([3-9]|[1-9][0-9]{1,2})(\.([0-9]|[1-9][0-9]{1,2})){1,2}$'; then
+    swan_ver_cur="$swan_ver_latest"
+  fi
+  [ -z "$SWAN_VER" ] && SWAN_VER="$swan_ver_cur"
+}
+
+check_swan_ver() {
+  if [ "$SWAN_VER" = "3.32" ] && [ "$os_ver" = "11" ]; then
+    exiterr "Libreswan 3.32 is not supported on Debian 11."
+  fi
+
+  if [ "$SWAN_VER" != "3.32" ] \
+    && { ! printf '%s\n%s' "4.1" "$SWAN_VER" | sort -C -V \
+    || ! printf '%s\n%s' "$SWAN_VER" "$swan_ver_cur" | sort -C -V; }; then
+cat 1>&2 <<EOF
+Error: Libreswan version '$SWAN_VER' is not supported.
+       This script can install one of these versions:
+       3.32, 4.1-$swan_ver_cur
+EOF
+    exit 1
+  fi
+}
+
 show_setup_info() {
 cat <<EOF
 
@@ -106,7 +117,7 @@ Note: This script will make the following changes to your VPN configuration:
 
 EOF
 
-  if [ "$SWAN_VER" != "4.6" ]; then
+  if [ "$SWAN_VER" != "$swan_ver_cur" ]; then
 cat <<'EOF'
 WARNING: Older versions of Libreswan could contain known security vulnerabilities.
          See https://libreswan.org/security/ for more information.
@@ -293,10 +304,8 @@ IMPORTANT: You must edit /etc/ipsec.conf and replace
            all occurrences of these two lines:
              modecfgdns1=DNS_SERVER_1
              modecfgdns2=DNS_SERVER_2
-
            with a single line like this:
              modecfgdns="DNS_SERVER_1 DNS_SERVER_2"
-
            Then run "sudo service ipsec restart".
 
 EOF
@@ -308,6 +317,8 @@ vpnupgrade() {
   check_vz
   check_os
   check_libreswan
+  get_swan_ver
+  check_swan_ver
   show_setup_info
   start_setup
   update_apt_cache