Brocade Communications Systems ServerIron ADX 12.4.00 - Manual (Page 162)

150 ServerIron ADX Global Server Load Balancing Guide
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Round-trip times
1
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.
Site-ServerIronADX# configure terminal

Site-ServerIronADX(config)# gslb agent-dns-prober
Syntax: gslb agent-dns-prober
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.
Site-ServerIronADX# configure terminal

Site-ServerIronADX(config)# gslb udp-probe-port 10000

Site-ServerIronADX(config)# reload
Syntax: gslb udp-probe-port <port-number>
Enter a number for <port-number>.
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 LDNS-host list update from the GSLB ServerIron ADX containing this
same prefix.
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.
SITE-ServerIronADX# configure terminal

SITE-ServerIronADX(config)# gslb agent-fast-age-icmp-fail
Syntax: [no] gslb agent-fast-age-icmp-fail
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.
SITE-ServerIronADX# configure terminal

SITE-ServerIronADX(config)# gslb agent-fast-age-dns-fail
Syntax: [no] gslb agent-fast-age-dns-fail