Brocade Virtual ADX Global Server Load Balancing Guide (Supporting ADX v03.1.00) - Manual (Page 168)

158 Brocade Virtual ADX Global Server Load Balancing Guide
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Advanced GSLB configuration for IPv6
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Round robin selection metric
The round robin selection metric is an alternative to the least response selection metric as the final
tie breaker. When you enable round robin selection, the GSLB Brocade Virtual ADX automatically
disables the least response selection metric, and instead uses the round robin algorithm to select
a site. Round Robin selection chooses the first IP address in the DNS response for the first client
request, then selects the next address for the next client request, and so on.
Use the round robin selection metric instead of the least response selection metric when you want
to prevent the GSLB Brocade Virtual ADX from favoring new or recently recovered sites over
previously configured active sites. The least response selection metric can cause the GSLB
Brocade Virtual 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 Brocade Virtual
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 Brocade Virtual 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 Brocade Virtual 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 on a
Brocade Virtual ADX, perform the following tasks:
1. Change the maximum virtual server system parameter to the maximum value supported on
the active license. Use the l4-virtual-server command.
2. Change the maximum real server system parameter to the maximum value supported on the
active license. Use the l4-real-server command.
3. Change the maximum server port parameter to the maximum value supported on the active
license. Use the l4-server-port command.
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
Brocade Virtual 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 Brocade Virtual ADX offers site sticky 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.
Sticky persistence enables the GSLB controller to ensure that the same IP address is sent to a
client sending multiple DNS requests within a configurable period of time. Site persistence is
particularly important in instances where user-specific content is stored at one site (such as a
shopping cart) and redirection to another site would result in a lost session. Sticky persistence
enables the GSLB controller to ensure that the client is directed to the site that was previously
visited.