Advanced GSLB configuration for IPv6 | 2 |
•You can bias a GSLB ServerIron ADX that is also configured as a site ServerIron ADX (for locally configured VIPs) to always favor itself as the best site. In this case, assign an administrative preference of 255 to the site for the GSLB ServerIron ADX itself, and assign a lower administrative distance to the other site ServerIron ADXs, or use the default (128) for those sites.
NOTE
The administrative preference metric is disabled by default and must be enabled before it is used in the GSLB policy algorithm. Once enabled, it is placed after the available session capacity metric. Refer to “Disabling or
Configuring administrative preference for a site
Once enabled, the default administrative preference for sites is 128. You can change the preference on an individual site basis.
Typically, you can set the administrative preference for a site ServerIron ADX when you define a site. For example, to set the administrative preference for a site ServerIron ADX to 255, enter a command such as the following:
ServerIronADX(config)# gslb site us
To change the preference for a site ServerIron ADX you have already configured, use the same command syntax. You do not need to reconfigure other site parameters when you change the preference. For example, to change the preference for a site ServerIron ADX from the default (128) to 200, enter a command such as the following:
ServerIronADX(config)# gslb site us
Least response selection metric
If multiple sites still compare equally based on all the metrics above, the GSLB ServerIron ADX selects the site that it has selected least often before. For example, if the GSLB ServerIron ADX has selected Site 1 and placed its IP address on top in 40% of the DNS replies, but has selected Site 2 60% of the time, then in this instance the GSLB ServerIron ADX selects Site 1. To display the response selection percentages for the sites you have configured, use the show gslb dns zone command. Refer to “Displaying DNS zone and hosts” on page 237.
This metric is a
Least response selection is enabled by default. You can disable the metric only by enabling the round robin selection metric to act as the tie breaker instead. See the following section.
Round robin selection metric
The round robin selection metric is an alternative to the least response selection metric as the final tie breaker. When you enable round robin selection, the GSLB ServerIron ADX automatically disables the least response selection metric, and instead uses the round robin algorithm to select a site. Round Robin selection chooses the first IP address in the DNS response for the first client request, then selects the next address for the next client request, and so on.
ServerIron ADX Global Server Load Balancing Guide | 221 |
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