Brocade Communications Systems ServerIron ADX 12.4.00 Manual Manual page 136

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Host-level policies for site selection
Syntax: [no] round-robin
Enabling the Round-Trip-Time metric
You can enable the GSLB metric for the round-trip time between the remote ServerIron ADX and the
DNS client.
The Round-trip time (RTT) is the amount of time that passes between when the remote site initiates
a TCP connection (sends a TCP SYN) to the client and when the remote site receives the client's
acknowledgment of the connection request (sends a TCP ACK). The GSLB ServerIron ADX learns
the RTT information from the site ServerIron ADXs through the GSLB protocol and uses the
information as a metric when comparing site IP addresses. The GSLB ServerIron ADX uses this
metric when evaluating the sites in a DNS reply to choose the best site.
You can enable or disable the Round Trip Time (RTT) metric and configure RTT tolerance for the
host-level policy. You can configure other parameters for the global GSLB policy, but not for the
host-level policy. If a host-level policy is applied to a host/zone, then the GSLB ServerIron ADX will
use the values defined in the global GSLB policy for RTT parameters that cannot be configured
under the host-level policy. These parameters are:
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•
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To enable the Round Trip Time metric for the host-level policy, enter commands such as the
following:
GSLB-ServerIronADX(config)# gslb-host-policy abc
GSLB-ServerIronADX(config-gslb-host-policy-abc)# round-trip-time
Syntax: [no] round-trip-time
Changing the RTT tolerance
To change the RTT tolerance for the host-level policy, enter commands such as the following:
GSLB-ServerIronADX(config)# gslb-host-policy abc
GSLB-ServerIronADX(config-gslb-host-policy-abc)# round-trip-time tolerance 20
Syntax: [no] round-trip-time tolerance <num>
Enabling the weighted IP metric
The weighted IP metric provides a way for the ServerIron ADX to distribute GSLB traffic among IP
addresses in a DNS reply, based on weights assigned to the IP addresses.
To enable weighted IP for the host-level policy, enter commands such as the following:
GSLB-ServerIronADX(config)# gslb-host-policy abc
GSLB-ServerIronADX(config-gslb-host-policy-abc)# weighted-ip
Syntax: [no] weighted-ip
Use the no form of the command to disable the weighted IP metric for the host-level policy.
Enabling the weighted site metric
The weighted site metric provides a way for the ServerIron ADX to distribute SLB traffic among
GSLB sites based on weights configured for the sites.
To enable the weighted site metric for a host-level policy, enter commands such as the following:
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RTT cache interval
RTT cache prefix length
RTT explore percentage
ServerIron ADX Global Server Load Balancing Guide
53-1002437-01