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If neither of these commands is configured, then the GSLB ServerIron ADX will not use any DNS probe measurement reported by the Site ServerIron ADXs and will use only the RTT values reported by the ICMP probe for the best IP address selection.
Enabling the DNS prober
To enable the DNS prober on the Site ServerIron ADX, enter the following on the Site ServerIron ADX.
Syntax: gslb
Sending DNS probes on a different port
By default Site ServerIron ADX sends DNS probes on port 9990. To send the probe on a different port, enter commands such as the following on the Site ServerIron ADX.
Syntax: gslb udp-probe-port <port-number>
Enter a number for
NOTE
A reload on the ServerIron ADX is required for this command to take effect.
Aging out prefixes when ICMP probe fails
You can instruct the Site ServerIron ADX to quickly age out a cache prefix for an LDNS host from the active RTT cache if an ICMP probe or a DNS probe to an LDNS host fails. Once the prefix is aged out, the Site ServerIron ADX collects RTT values from a different LDNS host for that prefix after it receives the next prefix or
To quickly age out prefixes from the active RTT cache on the Site ServerIron ADX when the ICMP probe to that LDNS host fails, enter the following on the Site ServerIron ADX.
Syntax: [no] gslb
Aging out prefixes when DNS probe fails
To quickly age out prefixes from the active RTT cache on the Site ServerIron ADX when the DNS probe to those LDNS hosts fail, configure the following on the Site ServerIron ADX.
Syntax: [no] gslb agent-fast-age-dns-fail
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