Brocade Communications Systems 12.4.00 manual Enabling weighted hash-based Gslb persistence

1 Weighted distribution of sites with hash-based persistence

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.

80	ServerIron ADX Global Server Load Balancing Guide
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