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You can change these parameters on an individual basis.
To change the session-table capacity metric, enter commands such as the following:
ServerIronADX(config)# gslb policy
ServerIronADX(config-gslb-policy)# capacity threshold 99
Syntax: [no] capacity threshold <num>
The <num> parameter specifies the maximum percentage of a site ServerIron ADX's session table
that can be in use. If the ServerIron ADX's session table utilization if greater than the specified
percentage, the GSLB ServerIron ADX prefers other sites over this site. You can specify a
percentage from 0-100. The default is 90.
To change the session-table tolerance metric, enter commands such as the following:
ServerIronADX(config)# gslb policy
ServerIronADX(config-gslb-policy)# num-session tolerance 20
Syntax: [no] num-session tolerance <num>
The <num> parameter specifies the maximum percentage by which the session table utilization on
ServerIron ADXs at different sites can differ without the GSLB ServerIron ADX selecting one over the
other based on this metric. You can specify a tolerance from 0-100. The default is 10.
FlashBack speed metric
If multiple sites compare equally based on all the metrics above, the ServerIron ADX chooses a site
as the best one based on how quickly the GSLB ServerIron ADX received responses to health
checks to the site ServerIron ADX.
The GSLB ServerIron ADX uses a tolerance value when comparing the FlashBack speeds of
different sites. The tolerance value specifies the percentage by which the FlashBack speeds of the
two sites must differ in order for the ServerIron ADX to choose one over the other. The default
FlashBack tolerance is 10%. Thus, if the FlashBack speeds of two sites are within 10% of one
another, the ServerIron ADX considers the sites to be equal. However, if the speeds differ by more
than 10%, the ServerIron ADX prefers the site with the lower FlashBack speed.
FlashBack speeds are measured at Layer 4 for all TCP/UDP ports. For the application ports known
to the ServerIron ADX, the FlashBack speed of the application is also measured.
When the ServerIron ADX compares the FlashBack speeds, it compares the Layer 7
(application-level) FlashBack speeds first, if applicable. If the application has a Layer 7 health
check and if the FlashBack speeds are not equal, the ServerIron ADX is through comparing the
FlashBack speeds. If a host is associated with multiple applications, the GSLB ServerIron ADX uses
the slowest response time among the applications for the comparison. However, if only the Layer 4
health check applies to the application, or if further tie-breaking is needed, the ServerIron ADX then
compares the Layer 4 FlashBack speeds.
ServerIron ADX Global Server Load Balancing Guide
53-1002437-01
Session capacity threshold: Specifies how close to the maximum session capacity the site
ServerIron ADX (remote ServerIron ADX) can be and still be eligible as the best site for the
client. This mechanism provides a way to shift load away from a site before the site becomes
congested. The default value for the threshold is 90%. Thus a site ServerIron ADX is eligible to
be the best site only if its session utilization is below 90%.
Available session capacity tolerance: Specifies the percentage by which the number of
available sessions on the site ServerIron ADX can differ from the number of available sessions
on another site ServerIron ADX and still be considered an equally good site.
Advanced GSLB configuration for IPv6
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