Tweak

Author: christiankuhtz

articles/load-balancer/load-balancer-custom-probe-overview.md

@@ -180,6 +180,11 @@ If all probes for all instances in a backend pool fail, existing UDP flows will
 
 All Load Balancer health probes originate from the IP address 168.63.129.16 as their source.  When you bring your own IP addresses to Azure's Virtual Network, this health probe source IP address is guaranteed to be unique as it is globally reserved for Microsoft.  This address is the same in all regions and does not change. It should not be considered a security risk because only the internal Azure platform can source a packet from this IP address. 
 
+In addition to Load Balancer health probes, the following operations use this IP address:
+
+- Enables the VM Agent to communicating with the platform to signal it is in a “Ready” state
+- Enables communication with the DNS virtual server to provide filtered name resolution to customers that do not define custom DNS servers.  This filtering ensures that customers can only resolve the hostnames of their deployment.
+
 For Load Balancer's health probe to mark your instance up, you **must** allow this IP address in any Azure [Security Groups](../virtual-network/security-overview.md) and local firewall policies.
 
 If you don't allow this IP address in your firewall policies, the health probe will fail as it is unable to reach your instance.  In turn, Load Balancer will mark down your instance due to the health probe failure.  This can cause your load balanced service to fail.