52 ServerIron ADX Global Server Load Balancing Guide
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Configuring GSLB protocol parameters
1
You can chan ge th ese p aram eter s 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.
Changing the FlashBack tolerance values
You can modify the following FlashBack parameters:
•Application tolerance
•TCP toleran ce
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. 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.
To change the tolerances for the response times of TCP and application health checks, when used
as a metric for selecting a site, enter commands such as the following:
ServerIronADX(config)# gslb policy
ServerIronADX(config-gslb-policy)# flashback application tolerance 30
ServerIronADX(config-gslb-policy)# flashback tcp tolerance 50
Syntax: [no] flashback application | tcp tolerance <num>
The application | tcp parameter specifies whether you are modifying the tolerance for the Layer 4
TCP health check or the Layer 7 application health checks. You can change one or both and the
values do not need to be the same. For each, you can specify from 0-100. The default for each is
10.