diff --git a/templates/scripts/includes/check-for-network b/templates/scripts/includes/check-for-network
index 1d88286..a83e276 100755
--- a/templates/scripts/includes/check-for-network
+++ b/templates/scripts/includes/check-for-network
@@ -15,13 +15,10 @@ EXIT_CODE=1
 
 GW="$(route -n | awk '/^0\.0\.0\.0/{print $2}')"
 GWDEV="$(route -n | awk '/^0\.0\.0\.0/{print $NF}')"
-NMAP="$(nmap -sP --host_timeout 4000 --max_rtt_timeout 4000ms "$GW" 2>/dev/null)"
 
-if [ $? -eq 0 ]; then
-  if ! echo "$NMAP" | grep -q "0 hosts up" ; then
-    STATUS="Online (${GWDEV})"
-    EXIT_CODE=0
-  fi
+if ping -c 3 "${GW}" >/dev/null ; then
+  STATUS="Online (${GWDEV})"
+  EXIT_CODE=0
 fi
 
 printf "%s\n" "$STATUS"
diff --git a/templates/scripts/includes/check_installing_version.sh b/templates/scripts/includes/check_installing_version.sh
index da601fa..7cd1627 100755
--- a/templates/scripts/includes/check_installing_version.sh
+++ b/templates/scripts/includes/check_installing_version.sh
@@ -37,13 +37,11 @@ if checkBootParam ngcppro ; then
   if checkBootParam "sipwiserepo=" ; then
     SIPWISE_REPO_HOST=$(getBootParam sipwiserepo)
   fi
+
   URL="${SIPWISE_REPO_TRANSPORT}://${SIPWISE_REPO_HOST}/sppro/"
-  accessible=$( curl -s -o /dev/null -w "%{http_code}" "${URL}" 2>/dev/null || true )
   err_message="You are installing Pro/Carrier version but ${SIPWISE_REPO_TRANSPORT}://${SIPWISE_REPO_HOST}/sppro/ repository not accessible. Please contact support@sipwise.com"
-  while [[ "${accessible}" != 200 ]]; do
-    if dialog --yes-label Retry --no-label Exit --yesno "${err_message}" 0 0 ; then
-      accessible=$( curl -s -o /dev/null -w "%{http_code}" "${URL}" 2>/dev/null || true )
-    else
+  while ! wget -q -T 10 -O /dev/null "${URL}" ; do
+    if ! dialog --yes-label Retry --no-label Exit --yesno "${err_message}" 0 0 ; then
       exit 1
     fi
   done
diff --git a/templates/scripts/includes/install_required_packages.sh b/templates/scripts/includes/install_required_packages.sh
new file mode 100755
index 0000000..f1964ac
--- /dev/null
+++ b/templates/scripts/includes/install_required_packages.sh
@@ -0,0 +1,9 @@
+#!/bin/bash
+
+set -e
+
+echo "Updating list of packages..."
+apt-get update 1>/dev/null
+echo "Installing required packages..."
+apt-get install --assume-yes \
+  isomd5sum
diff --git a/templates/scripts/includes/verify_iso_image.sh b/templates/scripts/includes/verify_iso_image.sh
index 3e399ad..829b24d 100755
--- a/templates/scripts/includes/verify_iso_image.sh
+++ b/templates/scripts/includes/verify_iso_image.sh
@@ -4,8 +4,6 @@ set -e
 
 message="Do you want to check the install media?"
 if dialog --yes-label Yes --no-label Skip --yesno "${message}" 0 0 ; then
-  sudo apt-get update 1>/dev/null || true
-  sudo apt-get install isomd5sum --assume-yes 1>/dev/null || true
   if ! result="$( { checkisomd5 /dev/sr0 1>/dev/null; } 2>&1 )" ; then
     err_message="Integrity check failed. Reason: ${result}. Abort installation or continue anyway?"
     if dialog --yes-label Exit --no-label Continue --yesno "${err_message}" 0 0 ; then
diff --git a/templates/scripts/main.sh b/templates/scripts/main.sh
index e06d9f3..ffacefd 100755
--- a/templates/scripts/main.sh
+++ b/templates/scripts/main.sh
@@ -145,6 +145,7 @@ deploy() {
 install_sipwise_keyring
 "${scripts_dir}/network_configuration.sh"
 "${scripts_dir}/check_installing_version.sh"
+"${scripts_dir}/install_required_packages.sh"
 "${scripts_dir}/verify_iso_image.sh"
 prompt_for_target
 check_for_existing_pvs