Networking

Fundamentals of Azure Internal Load balancers by Bruno Terkaly 

1. Internal load balancing (ILB) enables you to run highly available services behind a private IP address
2. Internal load balancers are only accessible only within a cloud service or Virtual Network (VNet)
   • This provides additional security on that endpoint.

Some questions I am hearing

1. I am able to access internal load balancer using IP address but not via load balancer or service name?
   • See Accessing the ILB below
2. Is there any option on Azure portal to view load balancer configuration?
   • Internal load balancing cannot be configured through the portal as of today, this will be supported in the future
   • However, it can be configured using powershell cmdlets.
     • ILB can be used in a deployment inside a Regional Virtual Network as well in a new deployment that is outside the Virtual Network
3. How do I monitor the traffic and which server it is redirecting it to?
4. How do I setup the probing and rules/alerts for it?
   • See the links below

ILB ENABLES THE FOLLOWING NEW TYPES OF LOAD BALANCING:

1. Between virtual machines within a cloud service.
2. Between virtual machines in different cloud services that are themselves contained within a virtual network.
3. Between on-premises computers and virtual machines in a cross-premises virtual network.

Some diagrams

EXAMPLE OF A MULTI-TIER APPLICATION USING WEB SERVERS AS THE FRONT END AND DATABASE SERVERS AS THE BACK END IN A CLOUD SERVICE.

1. Multi-Tier Web App

   Figure 1: Architecture for a Multi-Tier Web App

ILB CAN PERFORM LOAD BALANCING FOR TRAFFIC FROM INTRANET CLIENTS

1. Traffic from clients on the on-premises network get load-balanced across the set of LOB servers running in a cross-premises virtual network
2. You don’t need a separate load balancer in the on-premises network or in the virtual network

   Figure 2: Architecture for an Intranet Network

LOAD BALANCING ON-PREMISES SERVER TRAFFIC

1. ILB also allows traffic from servers on the on-premises network to be load-balanced across virtual machines running in a cross-premises virtual network.

   Figure 3: Architecture for an On-Premises Network

FROM ON PREMISES

1. When used within a Virtual Network the ILB endpoint is also accessible from on-premises and other inter-connected VNets allowing some powerful hybrid scenarios

ACCESSING THE ILB

FROM INSIDE A CLOUD SERVICE

1. VMs inside a cloud service have private IP address spaces
2. You can talk to the ILB using this private IP address

FROM WITHIN A VIRTUAL NETWORK

1. A customer can specify a static VNet IP address
2. A customer can retrieve the load balanced IP is acquired from a virtual subnet
3. This allows you to be connected VNets through the secure IP Sec tunnel

Some useful links