Brocade Communications Systems ServerIron ADX 12.4.00 - Manual (Page 225)

ServerIron ADX Global Server Load Balancing Guide 213
53-1002437-01
Advanced GSLB configuration for IPv6
2
ftp.gslb.com 
VIP 2001:DB8::2 belongs to New York with a weight of 30 
VIP 2001:DB8::3 belongs to London with a weight of 20
Suppose that ten 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 five times
(50%), New York is selected three times (30%), and London is selected two times (20%).
Now suppose that five DNS requests are made to ftp.gslb.com. In this case, New York receives
three requests (60%), and London receives two 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.
To view the results of traffic distribution after configuring weighted site metrics, use the show gslob
traffic site command. Refer to
“Displaying results of traffic distribution for weighted sites” on
page 235.
Session capacity threshold metric
The GSLB protocol supplies statistics for the session tables on each site ServerIron ADX. The
session table contains an entry for each open TCP or UDP session on the site ServerIron ADX. Each
ServerIron ADX has a maximum number of sessions that it can hold in its session table. Through
the GSLB protocol, the GSLB ServerIron ADX learns from each remote ServerIron ADX the maximum
number of sessions and the number of available sessions on that ServerIron ADX.
The capacity threshold specifies how close to the maximum session capacity the site ServerIron
ADX (remote ServerIron ADX) can be and still be eligible as the best site for the client. This
mechanism provides a way to shift load away from a site before the site becomes congested.