Brocade Virtual ADX Global Server Load Balancing Guide (Supporting ADX v03.1.00) - Manual (Page 55)

Brocade Virtual ADX Global Server Load Balancing Guide 45
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Configuring GSLB protocol parameters
1
In order to implement the Active Bindings metric, the GSLB Brocade Virtual ADX processes
information it receives from an agent. For each VIP address on the agent Brocade Virtual ADX, the
agent reports the following information to the GSLB Brocade Virtual ADX:
• The virtual ports configured
• The number of active real servers bound to the virtual port
For each VIP of interest, the GSLB Brocade Virtual ADX stores the number of active bindings for the
respective application port.
If the agent is running a software image that does not support the Active Bindings metric, it does
not report any information specific to the Active Bindings metric. In this case, the default active
bindings value for each VIP residing on that site is 1 or 0, depending on the health status of the VIP.
If the VIP is active, the value is 10. If the VIP is not active, it is 0.
By default, the Active Bindings metric is disabled. When enabled, it is placed after the Num-Session
metric in the GSLB algorithm. You can change the metric order or enable or disable other metrics,
although we do not recommend this.
DNS response processing
When the Active Bindings metric is enabled, the GSLB Brocade Virtual ADX evaluates each IP
address in the DNS reply from the server, and selects the IP address with the highest number of
active bindings. The client subsequently makes an SLB request to that IP address.
Active bindings are calculated as follows:
• If the IP address is a VIP residing on a remote site that supports active bindings, then the
number of active bindings equals the number of active real servers bound for application
ports.
• If the IP address is a VIP residing on a remote site that is running older versions of the GSLB
agent software, and consequently does not support the Active Bindings metric, then the
number of active bindings for the IP address is 1 or 0, depending on the health of the VIP.
• If the IP address is a real server, then the number of active bindings for the IP address is 1 or 0,
depending on the health of the real server.
If all IPs or VIPs have zero active bindings, or if all IPs or VIPs have the same number of active
bindings, the GSLB Brocade Virtual ADX passes them on to the next step in the GSLB algorithm,
where the process of selecting the best IP address continues. Likewise, if two or more IP addresses
have the highest maximum value of active bindings, the GSLB Brocade Virtual ADX passes them on
to the next step in the GSLB algorithm.
Enabling active bindings
Active bindings are a measure of the number of active real servers bound to a Virtual IP address
(VIP) residing on a GSLB site. The GSLB Brocade Virtual ADX uses the Active Bindings metric to
select the best IP address for the client. The VIP with the highest number of active bindings is the
IP address preferred by the Active Bindings metric.
To configure the Active Bindings metric, enter the following command.
Virtual ADX(config-gslb-policy)#active-bindings
Syntax: [no] active-bindings
Displaying active binding information
To view active bindings for each IP address, enter the following command.
Virtual ADX#show gslb dns detail