ServerIron ADX Global Server Load Balancing Guide 207
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Advanced GSLB configuration for IPv6 2
NOTE
Brocade recommends that you always use the health check as the first metric. Otherwise, it is
possible that the GSLB policy will not select a “best” choice, and thus send the DNS reply
unchanged. For example, if the first metric is geographic location, and the DNS reply contains two
sites, one in North America and the other in South America, for clients in South America the GSLB
policy favors the South American site after the first comparison. However, if that site is down, the
GSLB policy will find that none of the sites in the reply is the “best” one, and thus send the reply
unchanged.
You cannot change the position of the least response selection or round robin selection metric,
whichever is enabled. The GSLB ServerIron ADX uses the least response selection or round robin
selection metric as a tie-breaker if the other comparisons do not result in selection of a “best” site.
To change the order, specify the metrics in the desired order by entering a command such as the
following:
ServerIronADX(config)# gslb policy
ServerIronADX(config-gslb-policy)# metric-order set health-check capacity
num-session flashback
This command changes the GSLB policy to the following:
•The health check results
•The session capacity threshold (capacity) of the site ServerIron ADX
•The available session capacity threshold (num-session) of the site ServerIron ADX
•The FlashBack speed of the site ServerIron ADX
•The least response selection (the site ServerIron ADX that has been selected less often than
others)
Two of the metrics, server health and geographic location, are not specified. As a result, these
metrics are not used when evaluating site IP addresses in the DNS responses.
Syntax: [no] metric-order set <list>
The <list> parameter is a list of the metrics you want to use, in the order you want the GSLB
ServerIron ADX to use them. The GSLB uses the metrics in the order you specify them. You can
specify one or more of the following:
•active bindings: The ServerIron ADX’s preference for the IP address with the highest number of
active bindings.
•capacity: The session capacity threshold of the site ServerIron ADX.
•flashback: The FlashBack speed (how quickly the GSLB receives the health check results) of
the site ServerIron ADX.
•geographic: The geographic location of the server.
•health-check: The Layer 4 and application health checks.
•num-session: The available session capacity of the site ServerIron ADX.
•preference: The administratively configured preference for the site ServerIron ADX.
•weighted ip: The administratively configured traffic distribution method for the ServerIron ADX.
•weighted site: The administratively configured traffic distribution method for the ServerIron
ADX.