Brocade Communications Systems 12.4.00 manual Gslb affinity for high availability

GSLB affinity for high availability 1

GSLB affinity for high availability

The GSLB Affinity feature configures the GSLB ServerIron ADX to always prefer a specific Site ServerIron ADX for queries from clients (or client LDNS servers) whose addresses are within a configured IP prefix. To configure affinity, you associate a site ServerIron ADX with an IP prefix. When the GSLB ServerIron ADX receives a query from a client (or client LDNS server) whose IP address is within this configured prefix, the GSLB ServerIron ADX examines the DNS reply for a virtual IP address (VIP) configured on the ServerIron ADX associated with this IP prefix. It selects this VIP as the optimal IP address for the querying client (or client LDNS).

The GSLB Affinity feature allows you to associate an IP prefix with a ServerIron ADX. Consider the example where, ServerIron ADX-1 is in a high availability (HA) configuration with ServerIron ADX-2. You associate an IP prefix 1.1.1.0/24 with ServerIron ADX-1 using the existing affinity configuration command. You also configure VIP-1 on ServerIron ADX-1 where it is in the active state, and on ServerIron ADX-2 where it is in the standby state. VIP-1 is also one of the IP addresses configured for domain www.foo.com for which the GSLB ServerIron ADX is providing GSLB.

If a client in the 1.1.1.0/24 network sends a query for www.foo.com, the GSLB ServerIron ADX selects VIP-1 as the best IP address for the client, because the IP prefix 1.1.1.0/24 has been associated with ServerIron ADX-1 and VIP-1 is active on ServerIron ADX-1.

Now if a failover occurs between ServerIron ADX-1 and ServerIron ADX-2, VIP-1 becomes active on ServerIron ADX-2 and standby on ServerIron ADX-1. If a client (or client LDNS) in the 1.1.1.0/24 network queries for www.foo.com, the GSLB ServerIron ADX will no longer select VIP-1 as the optimal address based on the affinity configuration. The reason is that the affinity for 1.1.1.0/24 is configured for ServerIron ADX-1 but VIP-1 is no longer active on ServerIron ADX-1 but is active on ServerIron ADX-2. Since there is no affinity definition associated with ServerIron ADX-2, GSLB ServerIron ADX is unable to use it for best IP address selection.

There is flexibility in defining GSLB high availability groups that include ServerIron ADXs in any supported HA topologies. You can configure affinity similar to that described above (that is, an IP address prefix will be associated with a ServerIron ADX). However if your configure an HA group for the ServerIron ADXs, GSLB ServerIron ADX will be able to detect the HA peer for the ServerIron ADX configured in the affinity definition. Also, GSLB ServerIron ADXs will be able to use the affinity definition for both the ServerIron ADXs in the HA group.

For example, in the example described above with ServerIron ADX-1 and ServerIron ADX-2 in HA configuration, IP prefix 1.1.1.0/24 is associated with ServerIron ADX-1. Also, an HA group consisting of ServerIron ADX-1 and ServerIron ADX-2 can now be configured. When a client (or client LDNS) in the 1.1.1.0/24 network queries for www.foo.com, the GSLB ServerIron ADX selects VIP-1 as the best IP address no matter where it is active (on ServerIron ADX-1 or on ServerIron ADX-2, its peer ServerIron ADX configured in the HA group).

Configuring an HA group

Before configuring a GSLB HA Group, make sure the Site ServerIron ADXs that you want to place in the HA group have been configured.

Once Site ServerIron ADXs have been configured, you can configure an HA group that consists of two Site ServerIron ADXs by entering the following commands on the GSLB ServerIron ADX.

ServerIronADX# configure terminal

ServerIronADX(config)# gslb ha-group 1.1.1.55 1.1.1.65

ServerIronADX(config)# end

ServerIron ADX Global Server Load Balancing Guide	157
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