When deploying an application using the Microsoft Azure Infrastructure as a Service (IaaS) offering, you usually need to provide load balancing and other application delivery functions such as content switching, SSL Termination and IPS. Some of this functionality may also be necessary when deploying applications in Microsoft Azure Platform as a Service (PaaS). The LoadMaster for Azure enables you to address your needs of application delivery and High Availability (HA).

Deploying a single LoadMaster for Azure does not provide you with the high availability you need for your applications. When deploying a pair of LoadMasters in Azure, you can achieve high availability for your application. This document provides the details for a HA LoadMaster solution.

When using LoadMaster in High Availability on Azure, HA operates in much the same way as it does on non-cloud platforms, but with some key differences, which are listed below:

  • LoadMaster HA for Azure involves two LoadMasters that synchronize settings bi-directionally. Changes made to the active unit are replicated to the standby unit and changes made to the standby unit are replicated to the active unit.
  • The replication (synchronization) of settings (from active to standby) is not instant in all cases and may take a few moments to complete.
  • When synchronizing the GEO settings from active to standby, any Fully Qualified Domain Name (FQDN) or cluster IP addresses that match the active unit IP address are replaced with the standby unit IP address. Likewise, when synchronizing from standby to active, the standby unit IP address is replaced with the active unit IP address.
  • All user-defined settings are synchronized, with the exception of the following:
    • Default gateway (both IPv4 and IPv6)
    • IP addresses and netmasks
    • Hostname
    • Name server
    • Domain
    • Admin default gateway
    • Administrative certificate settings (.cert, .pem and .setadmin files)
    • Network interface settings: Link Status (Speed and Duplex), MTU and additional addresses
    • Virtual LAN (VLAN) configuration
    • Virtual Extensible LAN (VXLAN) configuration
    • Additional routes
  • The cloud HA LoadMaster does not have a "force update" option.
  • By default, the active unit is always set as active and the standby unit can be standby or active if the active unit fails. The active unit is active and never becomes the standby, even if it fails. Similarly the standby unit never becomes the active unit. When the active unit comes back up it is set as active and connections are automatically directed to the active again. Either the active or standby unit can be active or standby.
  • The HA Check Port must be set to the same port on both the active and standby units for HA to work correctly.
  • Depending on the design of the Network Security Groups, you must ensure the necessary ports are open inbound to allow for the traffic.

A complete description of non-cloud LoadMaster HA can be found in the High Availability (HA), Feature Description document.

For details on all of the supported configurations regarding multiple Public IP addresses along with multiple interfaces, refer to the following Knowledge Base article: Supported Network Configurations for LoadMaster in Azure.