diff --git a/Installation.md b/Installation.md
index 2ce0753..66cbf9b 100644
--- a/Installation.md
+++ b/Installation.md
@@ -78,3 +78,9 @@ After that, you should be able to access /nlvmi with a webbrowser. Create a new
 
 Do not forget to load the tun and tap kernel modules on the nodes.
 
+It might also be necessary to open up ports on the firewall.
+On Centos this could be used to do so:<br/>
+```firewall-cmd --zone=public --add-port=5700-6000/tcp --permanent```<br/>
+```firewall-cmd --reload```<br/>
+
+