Brocade Communications Systems ServerIron ADX 12.4.00 Manual Manual page 55

TABLE 5
GSLB site
San Jose
New York
London
Total
Now consider the example in
metrics (second column) does not equal 100. However, as illustrated in the last column, the GSLB
ServerIron ADX uses relative percentages in order to achieve 100% total weight distribution.
TABLE 6
IP address
San Jose
New York
London
Total
By default, the weighted site metric is disabled. When enabled, it is placed second in the GSLB
algorithm, after the Health Check metric. You can change the metric order and enable or disable
other metrics, although we do not recommend this. For more information, refer to
order of GSLB policy metrics"
DNS response processing
When the weighted site metric is enabled, the GSLB ServerIron ADX selects an IP address
belonging to a particular site to be the best IP address in the DNS reply to a client. The client
subsequently makes an SLB request to that IP address.
Using the weighted site metric, the GSLB algorithm calculates a relative weight for each IP address
and selects the IP address with the least relative weight. The GSLB ServerIron ADX uses the
following criteria to calculate the relative weight of an IP address:
•
•
•
If an IP address has a relative weight of zero, or if an IP address belongs to a site that does not have
an assigned weight, the IP address is not selected as the best IP address for a client. Note that all
real servers have a relative weight of zero, as do VIPs that belong to sites with no assigned weights.
If two or more IP addresses have the same relative weight, or if all of the IP addresses have a
relative weight of zero, all of the IP addresses with the same relative weight are passed on to the
next step in the GSLB algorithm, where the process of selecting the best IP address continues.
ServerIron ADX Global Server Load Balancing Guide
53-1002437-01
Example weighted site metric configuration
Table
Example weighted site metric configuration
The number of times the GSLB ServerIron ADX selected the IP address as the best IP address
to reply to a client
The number of eligible IP addresses to be evaluated by the weighted site metric, and the
weights of sites to which they belong
A calculated weight assigned to an IP address, based on the following criteria:
•
If the IP address is a real server, then the calculated weight is zero
•
If the IP address is a Virtual IP (VIP), the weight is calculated based on the site the VIP
belongs to, the weight of the site, and the number of candidate VIPs belonging to the site
and being evaluated by the weighted site metric
Configuring GSLB protocol parameters
Configured weighted site metric
50
30
20
100
6. In this example, the total of the Configured weighted site
Configured weighted site metric
15
20
10
45
on page 37.
Relative weighted site metric
50%
30%
20%
100%
Relative weighted site metric
33% (15/45 * 100)
44% (20/45 * 100)
22% (10/45 * 100)
100%
"Changing the
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