Brocade Virtual ADX Global Server Load Balancing Guide (Supporting ADX v03.1.00) - Manual (Page 182)

172 Brocade Virtual ADX Global Server Load Balancing Guide
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Displaying GSLB for IPv6 configurations
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Clearing DNS selection counters
The GSLB Brocade Virtual ADX maintains DNS selection statistics for each IP address based on
DNS requests served for a particular domain name. These DNS selection statistics include:
• How many times the IP address was selected as the best IP address
• Which metrics were used for making the IP address selection
• The percentage of times an IP address was selected in comparison with other IP addresses in
the same domain name
Use the show gslb dns zone command to display the DNS selection statistics.
DNS selection statistics are used to implement GSLB metrics such as least response, weighted site
and weighted IP metrics. Each of these metrics base subsequent selections on the number of
times the IP address was previously selected. For example, the weighted site metric selects the IP
address that has the least relative weight, the calculation of which is based on the selection
counter of that IP address.
It can be advantageous to use the clear DNS selection counters feature in conjunction with GSLB
metrics. Consider the following examples:
• The least response selection metric selects the IP address that has been selected the least
number of times when compared to other IP addresses. If an IP address has become available
after having been down for some time, it might suddenly become flooded with subsequent
traffic because its selection counter is low. Clearing the counters for that zone can prevent a
flood to this IP address.
• You can also use this feature to test the GSLB implementation before deploying it on a wider
scale. You can analyze the effectiveness of each GSLB metric by rearranging the metric order
and using the Clear Counters feature to start over without having to reload the software.
To clear DNS selection counters globally or per zone, without reloading the software, or to clear out
any DNS requests for any client, enter a command such as the following:
Virtual ADX#clear gslb dns zone zone1
Syntax: clear gslb dns zone-name [name]
Replace zone-name with the zone for which you want to clear the DNS selection counters. To clear
the counters globally (for all zones), do not enter a zone-name.
Displaying detailed DNS information
Use the show gslb dns detail command to view detailed information about the DNS zones and host
names on GSLB controllers. Using this command, you can view key information about a zone
including its IP list and selection criteria as well as information about the site and Brocade Virtual
ADX on which a VIP is configured.
The command can be used with or without the zone-name variable, which specifies a single zone. If
this variable is omitted, all zones are displayed.