222 ServerIron ADX Global Server Load Balancing Guide
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Advanced GSLB configuration for IPv6
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Use the round robin selection metric instead of the least response selection metric when you want
to prevent the GSLB ServerIron ADX from favoring new or recently recovered sites over previously
configured active sites. The least response selection metric can cause the GSLB ServerIron ADX to
select a new site or a previously unavailable site that has come up again instead of previously
configured sites for a given VIP. This occurs because the GSLB ServerIron ADX has selected the
new site fewer times than previously configured sites for the VIP.
In some cases, the least response selection metric can cause the GSLB ServerIron ADX to send
client requests to a new or recovered site faster than the site can handle while it is coming up. To
avoid this situation, you can configure the GSLB ServerIron ADX to use the round robin selection
metric instead of the least response selection metric as the final tie breaker.
The round robin selection metric is disabled by default.
Check the current and maximum values for GSLB resources using the show gslb resource
command. If you are configuring more than 256 zones or configuring more than 600 hosts,
perform the following tasks:
1. Change the maximum virtual server system parameter to the maximum value supported in the
current release. Use the l4-virtual-server command.
For the current maximum virtual server value supported, see the table named "The Number of
Supported Real Servers, Virtual Servers and Ports" in the ServerIron ADX Server Load
Balancing Guide.
2. Change the maximum real server system parameter to the maximum value supported in the
current release. Use the l4-real-server command.
For the current maximum real server value supported, see the table named "The Number of
Supported Real Servers, Virtual Servers and Ports" in the ServerIron ADX Server Load
Balancing Guide.
3. Change the maximum server port parameter to the maximum value supported in the current
release. Use the l4-server-port command.
For the current maximum server port value supported, see the table named "The Number of
Supported Real Servers, Virtual Servers and Ports" in the ServerIron ADX Server Load
Balancing Guide.
4. Check your system parameter values using the show default value CLI command.
NOTE
The sum of number of VIPs configured and the number of GSLB hosts configured on the GSLB
ServerIron ADX should not exceed 1024. Similarly, the sum of real servers configured and the
number of DNS IP addresses should not exceed 4096.
Sticky persistence for IPv6
GSLB ServerIron ADX offers two methods for site persistence: sticky persistence and hash-based
persistence. Sticky persistence is the best solution for site persistence in single-box and High
Availability (hot standby, symmetric active-standby, symmetric active-active) topologies.