Brocade Communications Systems ServerIron ADX 12.4.00 Manual Manual page 56

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Configuring GSLB protocol parameters
Traffic distribution specifications
In general, DNS response selection counters are maintained per IP address, per domain name. For
example, suppose you configure three GSLB sites with assigned weights. All three sites host the
application www.gslb.com and sites New York and London also host ftp.gslb.com, as illustrated
below.

www.gslb.com
VIP 1.1.1.1 belongs to San Jose with a weight of 50
VIP 1.1.1.2 belongs to New York with a weight of 30
VIP 1.1.1.3 belongs to London with a weight of 20
ftp.gslb.com
VIP 1.1.1.2 belongs to New York with a weight of 30
VIP 1.1.1.3 belongs to London with a weight of 20
Suppose that 10 DNS requests are made to www.gslb.com. By viewing the selection counters
(using the show gslb dns zone command), you would see that San Jose is selected 5 times (50%),
New York is selected 3 times (30%), and London is selected 2 times (20%).
Now suppose that 5 DNS requests are made to ftp.gslb.com. In this case, New York receives 3
requests (60%), and London receives 2 requests (40%). This is because counters are maintained
per IP address per domain name.
If you consider the total site traffic for both applications, the traffic distribution is as follows: San
Jose = 5 (33%); New York = 6 (40%); and London = 4 (26%). The GSLB ServerIron ADX evaluates
the results of the weighted metrics with respect to a specific domain name, not an IP address
alone.
Configuring weighted site metrics
To configure weighted site metrics, complete the following tasks.
1. Enable the weighted site metric.
2. Select the site for which to apply weights.
3. Configure a weight for the site.
For example, enter commands such as the following:
ServerIronADX(config-gslb-policy)# weighted-site
ServerIronADX(config-gslb-policy)# gslb site SanJose
ServerIronADX(config-gslb-site-SanJose)# weight 50
Syntax: [no] weighted-site
Syntax: gslb site <site name>
The <site name> can have a maximum of 16 characters.
Syntax: weight <weight>
The <weight> is a value from 0 to 100. The default value is 0.
44 ServerIron ADX Global Server Load Balancing Guide
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