Brocade Virtual ADX Global Server Load Balancing Guide (Supporting ADX v03.1.00) - Manual (Page 96)

86 Brocade Virtual ADX Global Server Load Balancing Guide
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Host-level policies for site selection
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• 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 Brocade Virtual 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
Brocade Virtual 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 Brocade
Virtual ADX, the Brocade Virtual ADX sends the DNS reply unchanged to the client.
To configure the Brocade Virtual ADX to remove IP addresses from DNS replies when those
addresses fail a health check, enter commands such as the following.
Virtual ADX(config)#gslb host-policy abc
Virtual ADX(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 Brocade Virtual 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 Brocade Virtual 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.
Virtual ADX(config)#gslb host-policy abc
Virtual ADX(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.
Changing the TTL for DNS records
When the Brocade Virtual ADX receives a DNS query for a GSLB host configured in a GSLB zone, it
sends the TTL configured under the GSLB global policy in the DNS response to the client. By
default, all hosts configured under a GSLB zone use the same TTL for different domain names.