diff --git a/README.md b/README.md
index 3c05483..0adbbce 100644
--- a/README.md
+++ b/README.md
@@ -18,4 +18,9 @@ test connection: ansible -m ping --ask-vault-pass --extra-vars '@passwd.yml' TAR
 
 run playbook: ansible-playbook --ask-vault-pass --extra-vars '@passwd.yml' setup-pb.yml -l TARGET_IP OR NAME -u root
 
-Reference: https://www.vultr.com/docs/how-to-configure-a-new-ubuntu-server-with-ansible/
\ No newline at end of file
+Reference: https://www.vultr.com/docs/how-to-configure-a-new-ubuntu-server-with-ansible/
+
+modify /etc/sysctl.conf, add the line:
+net.ipv4.icmp_echo_ignore_all = 1  #don't respond to pings
+
+and then: sudo sysctl -p