Brocade Virtual ADX Global Server Load Balancing Guide (Supporting ADX v03.1.00) - Manual (Page 107)

Brocade Virtual ADX Global Server Load Balancing Guide 97
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Geographic region for a prefix
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Geographic region for a prefix
Brocade’s GSLB policies use a number of metrics, including the geographic location of a server, to
evaluate the server IP addresses in a DNS reply.
The GSLB Brocade Virtual ADX uses the Internet Assigned Numbers Authority’s (IANA’s) IP address
prefixes (IPv4 or IPv6) to generate an initial static database of geographic prefixes. This database
consists of IP address prefixes (IP address/prefix length) and their corresponding geographic
locations, such as, the continent for each IP address prefix.
You can configure the geographic locations for an IP address prefix, or override an existing
geographic region for an IP address prefix by configuring a new one. You can assign one of the
following geographic locations to an IP address prefix:
• North America
• South America
• Europe
• Asia
How geographic location is determined
Once you configure a geographic region for an IP address prefix, the GSLB Brocade Virtual ADX
determines the geographic region of a server in the following ways:
• For a real IPv4 or IPv6 address (as opposed to a Virtual IP address (VIP), which is a logical IP
address configured on a site ADX device), the geographic region is based on the IP address. If
you configure a geographic prefix that matches the real server IP address, the device obtains
the geographic location of the real server from the geographic prefix entry that you configure.
• For a VIP, the geographic region is based on the management IP address of the site ADX device
on which the VIP is configured. If you configure a geographic prefix that matches the
management IP address of the site ADX device on which the VIP is configured, the device
obtains the geographic location of the VIP from the geographic prefix entry that you configure.
• You can explicitly specify the region for a GSLB Site if the management IP address of the
remote ADX device at that Site is not indicative of the geographic location. To do so, use the
geo-location command. .
For example, if the management IP address is in a private subnet, the address is not indicative
of the Brocade Virtual ADX’s geographic location. If you specify the region for the GSLB Site,
the GSLB Brocade Virtual ADX uses the region you specify instead of the region of the Brocade
Virtual ADX’s management IP address.
If you configure a geographic prefix entry that matches the management IP address of the
remote ADX device and also specify a geographic location for the GSLB Site where the remote
ADX device resides, then the geographic location configured for the GSLB Site takes
precedence over the one defined in the user-configured geographic prefix entry. For example,
the geographic region for a VIP configured on the remote ADX device will be obtained from the
geographic location configured for the GSLB Site where the remote ADX device resides instead
of the geographic prefix entry that matches the management IP address of the remote ADX
device.