Brocade Communications Systems ServerIron ADX 12.4.00 - Manual (Page 131)

ServerIron ADX Global Server Load Balancing Guide 119
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Host-level policies for site selection
1
You must specify a connection limit to enable the Connection Load metric. You can specify a value
from 1 to as high a value as you need. There is no default. However, the actual value of the
Connection Load limit, and other connection load parameters, will be obtained from the global
GSLB policy.
Other connection load parameters include the following:
• Sampling intervals and sample rate
• Interval weights
NOTE
If the Connection Load limit is not configured in a host-level GSLB policy, but is configured in the
global GSLB policy, and the host-level GSLB policy is applied to a host, the Connection Load metric
will not be used during the GSLB selection process for that host/zone. The Connection Load limit
configuration for the host-level GSLB policy serves as a way to enable or disable the Connection Load
metric for a host when it is enabled in the global GSLB policy.
Removing IP addresses that fail a health check from DNS replies
You can configure the ServerIron ADX to remove IP addresses from DNS replies, for those hosts to
which the host-level GSLB policy applies, when those addresses fail a health check. The ServerIron
ADX removes the addresses that fail the check so long as the DNS query still contains at least one
address that passes the health check.
A site must pass all applicable health checks (Layer 4 and Layer 7) to avoid being removed.
NOTE
If all the sites fail their health checks, resulting in all the sites being rejected by the GSLB ServerIron
ADX, the ServerIron ADX sends the DNS reply unchanged to the client.
To configure the ServerIron ADX to remove IP addresses from DNS replies when those addresses
fail a health check, enter commands such as the following:
ServerIronADX(config)# gslb host-policy abc

ServerIronADX(config-gslb-host-policy-abc)# dns active-only
Syntax: [no] dns active-only
Use the no form of the command to disable this DNS parameter.
Removing all IP addresses except the best address
By default, the GSLB ServerIron ADX retains the same number of IP addresses in the DNS replies
from the DNS server. The GSLB policy swaps the IP address on the top of the list with the “best”
address, selected by the GSLB policy.
You can configure the ServerIron ADX to remove all addresses except the one the host-level GSLB
policy selects as the best address, by entering commands such as the following:
ServerIronADX(config)# gslb host-policy abc

ServerIronADX(config-gslb-host-policy-abc)# dns best-only
Syntax: [no] dns best-only
Use the no form of the command to disable this DNS parameter.
NOTE
If the GSLB policy does not result in the selection of a “best” address, the DNS reply can still contain
multiple addresses.