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Fundamentals of Azure Internal Load balancers (ILBs)

  • Article

  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

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    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

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    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.

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    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

Regional Virtual Networks https://azure.microsoft.com/blog/2014/05/14/regional-virtual-networks/#
Internal Load Balancing https://azure.microsoft.com/blog/2014/05/20/internal-load-balancing/#
Configure an internal load-balanced set https://msdn.microsoft.com/en-us/library/azure/dn690125.aspx#
Azure Load Balancer https://msdn.microsoft.com/en-us/library/azure/dn655058.aspx#
Configure a load-balanced set https://msdn.microsoft.com/en-us/library/azure/dn655055.aspx#

Comments

  • Anonymous
    February 18, 2015
    How do you get the internal load balancer status? i.e. which VMs are currently servicing requests?

  • Anonymous
    April 14, 2015
    Same question as Ben here - how can we see the current status of the ILB, and which members are flagged as up/down? It would also be useful to see history here, to identify for example whether a particular member has been flapping.

  • Anonymous
    September 18, 2015
    The comment has been removed