Brocade Virtual ADX Global Server Load Balancing Guide (Supporting ADX v03.1.00) - Manual (Page 19)

Brocade Virtual ADX Global Server Load Balancing Guide 9
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Global Server Load Balancing overview
1
Active Bindings metric
You can configure the Brocade Virtual ADX to prefer an IP address with the highest number of
active bindings.
Active bindings are a measure of the number of active real servers bound to a Virtual IP address
(VIP) residing on a GSLB site. The GSLB Brocade Virtual ADX uses the Active Bindings metric to
select the best IP address for the client. The VIP with the highest number of active bindings is the
IP address preferred by the Active Bindings metric.
To configure Active Bindings metrics, refer to “Enabling the Active Bindings metric” on page 85.
Geographic location of the server
For each client query, the GSLB Brocade Virtual ADX can determine the geographic location from
which the client query came based on its IP address. The GSLB can determine whether the query
came from North America, Asia, Europe, or South America. If multiple sites compare equally based
on the metrics above, the GSLB Brocade Virtual ADX prefers sites within the same geographic
region as the client query.
NOTE
The GSLB Brocade Virtual ADX deduces the geographic region of the client’s local DNS server from
the destination IP address in the DNS reply, which is the address of the client’s local DNS server.
The GSLB Brocade Virtual ADX determines the geographic region of a server IP address in its DNS
database in the following ways:
• For real IP addresses (as opposed to VIPs, which are logical IP addresses configured on the
site ADX devices), the geographic region is based on the IP address itself.
• For VIPs, the geographic region is based on the management IP address of the site ADX device
on which the VIP is configured.
• You can explicitly specify the region if the management IP address of the remote Brocade
Virtual ADX is not indicative of the geographic location. For example, if the management IP
address is in a private subnet, the address does not indicate the Brocade Virtual ADX’s
geographic location. If you specify the region, the Brocade Virtual ADX uses the region you
specify instead of the region of the Brocade Virtual ADX’s management IP address.
Site ADX device’s connection load
A GSLB site’s connection load is the average number of new connections per second on the site,
over a given number of intervals. When you enable this GSLB metric, all potential candidates are
compared against a predefined load limit. All sites that have fewer average connections than the
threshold are selected and passed to the next comparison metric. The connection limit metric is
disabled by default but is enabled (added to the GSLB policy) when you configure the metric.