ServerIron ADX Global Server Load Balancing Guide 129
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Geographic region for a prefix 1
GSLB-ServerIronADX(config-gslb-dns-gslb1.com)# exit
GSLB-ServerIronADX(config)# gslb dns zone foo.com
GSLB-ServerIronADX(config-gslb-dns-foo.com)# host-info ftp ftp
GSLB-ServerIronADX(config-gslb-dns-foo.com)# host-info ftp gslb-policy test
In the above example, with host policy “test” applied to host “www” for gslb1.com, when the
ServerIron ADX receives client queries for www.gslb1.com, the GSLB ServerIron ADX returns only
the healthy IP addresses with the best IP address at the top of the list (i.e., 1.1.1.101 only).
Since the global GSLB policy is in effect for host "ftp" for gslb1.com, when the ServerIron ADX
receives client queries for ftp.gslb1.com, the GSLB ServerIron ADX will return all IP addresses for
this domain with the best IP address at the top of the list (i.e., it returns 1.1.1.78 and 1.1.1.76).
Geographic region for a prefix Brocade ServerIron ADX 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 ServerIron 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
•Africa
How geographic location is determined
Once you configure a geographic region for an IP address prefix, the GSLB ServerIron ADX
determines the geographic region of a server in the following ways:
•For a real IPv4 or IPv6 address, 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 virtual IP address— a logical IP address configured on a site ServerIron ADX, the
geographic region is based on the management IP address of the site ServerIron ADX on which
the VIP is configured. If you configure a geographic prefix that matches the management IP
address of the site ServerIron ADX on which the VIP is configured, the device obtains the
geographic location of the VIP from the geographic prefix entry that you configure.
•If the management IP address of the remote ServerIron ADX at that site is not indicative of the
geographic location, use the geo-location command to specify the region of the GSLB site. For
more information about this command, see “Specifying site locations” on page 20.
For example, if the management IP address is in a private subnet, the address is not indicative
of the ServerIron ADX’s geographic location. If you specify the region for the GSLB site, the
GSLB ServerIron ADX uses the region you specify instead of the region of the ServerIron ADX’s