ServerIron ADX Global Server Load Balancing Guide 223
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Advanced GSLB configuration for IPv6 2
NOTE
Hash-based persistence is a better choice for GSLB configurations that utilize two GSLB controllers
(that are not in an HA configuration) for the same domain and where site persistence is needed for
a single client that is directed to two GSLB controllers. For more information, see “Hash-based
persistence for IPv6” on page 225
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.
To return the same IP address for a client that has sent requests previously, the GSLB controller
must save the following information:
•Client IP address/prefix
•Domain name the client requested
•Selected IP address for the request
This information is saved in a session table when the sticky GSLB persistence is enabled, and the
GSLB controller creates a sticky session for each client within the session table. Each session has a
special user type and source port or destination port number to distinguish from other sessions.
When a new request enters the system, the GSLB controller searches for the client IP and domain
name pair. If a match is found, the previously selected IP address will be returned.
To ensure the selected IP is still valid for the request, the GSLB controller checks for the following
conditions to be true before it returns the reply:
•Selected IP still belongs to the requested domain
•Selected IP is still active
Enabling sticky persistence for IPv6
Sticky persistence for IPv6 addresses is implemented as a GSLB policy, and it can be applied
globally or on per-host basis.
To enable GSLB globally for all domains, enter commands such as the following on the GSLB
controller:
SLB-Ctrl-ServerIronADX(config)#gslb policy
SLB-Ctrl-ServerIronADX(config-gslb-policy)#sticky
To enable Sticky GSLB for a specific host, enter commands such as the following on the GSLB
controller:
SLB-Ctrl-ServerIronADX(config)#gslb-host-policy test
SLB-Ctrl-ServerIronADX(config-gslb-host-policy-test)#sticky
SLB-Ctrl-ServerIronADX(config)#gslb dns zone gslb.com
SLB-Ctrl-ServerIronADX(config-gslb-dns-gslb.com)#host-info www gslb-policy test
This example defines a host policy, then applies that policy to the specific host www. The sticky is
one function within the host policy.
Syntax: [no] sticky