Brocade Communications Systems ServerIron ADX 12.4.00 - Manual (Page 92)

80 ServerIron ADX Global Server Load Balancing Guide
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Weighted distribution of sites with hash-based persistence
1
NOTE
All the existing CLI for old hash-based persistence is applicable to weighted hash based persistence
also. It is not described in this document for the sake of brevity. For further details on existing CLI
for hash-based persistence, please refer to the online GSLB documentation.
Enabling weighted hash-based GSLB persistence
Weighted hash-based GSLB persistence can be enabled for all domains or for specific domains as
needed. User enables this feature in the global or host-level policy. As a result, this feature applies
to all the domains this policy is bound to. This feature cannot be enabled concurrently with Sticky
GSLB in the same policy. However you can enable Sticky GSLB for one policy and Weighted
hash-based GSLB persistence for another policy.
To enable Weighted hash-based GSLB persistence globally, enter commands on the GSLB
controller, such as the following:
ServerIronADX(config)# gslb policy
ServerIronADX(config-gslb-policy)# hash-persist weighted
To enable Weighted hash-based GSLB persistence for a host-level policy, enter commands on the
GSLB controller, such as the following:
ServerIronADX# config t
ServerIronADX(config)# gslb-host-policy test
ServerIronADX(config-gslb-host-policy-test)# hash-persist weighted
Syntax: [no] hash-persist [weighted]
NOTE
Note that "weighted" is an optional parameter. If "weighted" is not specified, then the old hash-based
persistence mechanism will be in effect. The old hash-based persistence mechanism distributes the
hash buckets in a round robin manner. If the mechanism is changed from hash-based persistence
to weighted hash-based persistence or vice versa in a GSLB global or host-level policy, then the hash
table for all domains associated with that policy will be rehashed.
GSLB hash based site persistence with configurable subnet mask length
ServerIron ADX allows specification of subnet mask while doing GSLB site persistence. The LB
controller hashes the entire 32-bits of a LDNS IP address to generate the hash bucket for GSLB
hash-based persistence. As a result, LDNS servers in the same subnet could be assigned to
different hash buckets. We now provide a mechanism for the user to define a subnet length for
hashing; only this portion of the LDNS IP address will be used to generate the hash bucket. As a
result, user can ensure that all the LDNS servers that fall in the same subnet, as defined by the
hash prefix length, will hash to the same bucket and be serviced by the same domain IP address.
As an example, if the specified source subnet mask is /24 then all LDNS servers within a given /24
subnet would receive same response (site IP) from the GSLB controller.
ServerIronADX(config)# gslb policy

ServerIronADX(config-gslb-policy)# prefix-len-hash-persist 24
Syntax: [no] prefix-len-hash-persist <length>
NOTE
This command should be configured under the gslb global or host-level policy.