KEMP vCloud Air - Manual (Page 14)

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VLM for VMware vCloud Air
Installation Guide
Configuring Global Site Load Balancing (GSLB)
When using the LoadMaster with vSphere Hybrid Cloud Service, ensure that the GEO
functionality is enabled. GEO can be enabled in the Global Balancing section of the main menu
in the LoadMaster WUI.
The LoadMaster GEO add-on provides the VLM with Global Server Load Balancing (GSLB)
capabilities. This enables multi-site HA and simplified disaster recovery across private cloud and
vCloud Air boundaries. Even when the primary site is down, traffic is diverted to an alternate
site. GEO also ensures that clients connect to their fastest performing and geographically closest
target as well as allowing for defined traffic distribution policies to be applied.
Workflow for Accessing Services Distributed with GEO
The workflow for accessing services distributed with GEO is outlined below:
1. When a client initiates a request for an application, the following actions take place to
achieve HA:
a) The client requests name resolution to access service or application.
b) The DNS entry for service or application (URL, for example web.example.com) is
delegated to VLM appliances:
In DNS zone files, the entry may look similar to the following:
Entry Name, TTL, Type, Data
Web.example.com, Default, NS, vlm1.example.com
Web.example.com, Default, NS, vlm2.example.com
c) The authoritative DNS Server for zone example.com forwards the resolution request
to the VLM appliances
2. The VLM uses GEO functionality to determine the health status of each participating
LoadMaster and Virtual Service along with the configured load balancing mechanism,
such as round robin or location based, to determine which target the request should
resolve to.
3. The client receives a response with the service IP to connect to.
4. The client application connects to the resolved IP address, the VLM forwards the request
to the application servers according to the configured load balancing mechanism and
server’s health state.
Setup DNS Integration/Delegation
Integrating the LoadMaster with your Authoritative DNS can be completed with only a few DNS
records:
1. Create a new A record which is pointed to the VLM, for example lm1.example.com.
Create the corresponding PTR record for the reverse lookup by IP. Forward-confirmed
reverse DNS support is required.