Brocade Virtual ADX Global Server Load Balancing Guide (Supporting ADX v03.1.00) - Manual (Page 99)

Brocade Virtual ADX Global Server Load Balancing Guide 89
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Host-level policies for site selection
1
NOTE
When both the Health Check metric and the Flashback metric are disabled for a host-level GSLB
policy, the GSLB Brocade Virtual ADX will not perform any Layer 4 or Layer 7 health checks for the
hosts/zones for which the policy applies.
Changing the order of the metrics
You can change the order in which the GSLB Brocade Virtual ADX applies the policy metrics for the
host-level policy. To change the order, specify the metrics in the desired order, such as the
following.
GSLB-Virtual ADX(config)#gslb-host-policy abc
GSLB-Virtual ADX(config-gslb-host-policy-abc)#metric-order set health-check
capacity num-session flashback
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 Brocade
Virtual ADX to use them for the host-level policy. The GSLB Brocade Virtual ADX uses the metrics in
the order you specify. You can specify one or more of the following:
• active bindings – The Brocade Virtual ADX’s preference for the IP address with the highest
number of active bindings
• capacity – The remote ADX session capacity threshold.
• connection-load – The site ADX device’s average number of new connections per second
• flashback – The site ADX device’s Flashback speed (how quickly the GSLB receives the health
check results)
• geographic – The geographic location of the server
• health-check – The Layer 4 and application health checks
• num-session – The remote ADX available session capacity
• order - The order of the IP addresses
• preference – The administratively configured preference for the site ADX device
• round-robin - The round-robin Selection metric as an alternative to the Least Response
Selection metric
• weighted ip – The administratively configured traffic distribution method for the Brocade
Virtual ADX based on weights for IP addresses
• weighted site – The administratively configured traffic distribution method for the Brocade
Virtual ADX based on weights for GSLB Sites
There are no parameters for the Least Response Selection or Round Robin Selection metrics.
These metrics are tie-breakers. Only one of them is enabled at a time and the one that is enabled
will always be the last metric in the host-level policy.
NOTE
We recommend 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.