Changing the order of gslb policy metrics – Brocade Communications Systems ServerIron ADX 12.4.00 User Manual
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ServerIron ADX Global Server Load Balancing Guide
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Configuring GSLB protocol parameters
1
After changing policy values, you can display the new values using the show gslb policy command.
If you decide you want to change a value back to its default (using “no” in front of the command you
used to change it), you can display all the default policy values by entering the show gslb default
command. Refer to
“Displaying the default GSLB policy”
NOTE
You also can configure the ServerIron ADX to intercept or directly respond to DNS queries instead of
evaluating responses from the authoritative DNS server. Refer to
“Transparent DNS query intercept”
Changing the order of GSLB policy metrics
You can change the order in which the GSLB ServerIron ADX applies the policy metrics.
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.
You cannot change the position of the least response selection or round robin selection metric,
whichever is enabled. The GSLB ServerIron ADX uses the least response selection or round robin
selection metric as a tie-breaker if the other comparisons do not result in selection of a “best” site.
To change the order, specify the metrics in the desired order, by entering a command such as the
following:
ServerIronADX(config)# gslb policy
ServerIronADX(config-gslb-policy)# metric-order set health-check round-trip-time
capacity num-session flashback
This command changes the GSLB policy to the following:
•
The health-check results
•
The round-trip time between the remote ServerIron ADX and the DNS client
•
The site ServerIron ADX’s session capacity threshold
•
The site ServerIron ADX’s remote SI session capacity threshold
•
The site ServerIron ADX’s FlashBack speed (how quickly the GSLB receives the health check
results)
•
The Least Response selection (the site ServerIron ADX that has been selected less often than
others)
Two of the metrics, server health and geographic location, are not specified. As a result, these
metrics are not used when evaluating site IP addresses in the DNS responses.
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
ServerIron ADX to use them. The GSLB uses the metrics in the order you specify them. You can
specify one or more of the following: