This article contains information about configuring and troubleshooting the static Global Server Load Balancing (GSLB) feature on a NetScaler appliance.
A NetScaler appliance with the GSLB feature directs DNS requests to the GSLB site with the best performance. When a client sends a DNS request, the appliance identifies the site with the best performance and sends the IP address of the site to the client. The appliance decides by using the Metric Exchange Protocol (MEP), GSLB policies, and GSLB methods supported by the appliance. The GSLB methods are algorithms that control how the appliance load balances the client requests across the distributed data centers.
You can configure the GSLB feature based on the round trip time (RTT), static proximity, or a combination of the two.
The static proximity feature uses an IP address-based static location database. This database contains GeoIP address and the information of the location to which the site belongs. When a user visits the website, GeoIP address can determine the information such as country, region, city, and longitude/latitude. The database used to implement the static proximity method often contains information of all the GSLB sites. The appliance uses this database to determine the proximity between the Local DNS (LDNS) of the client and the GSLB sites. The appliance sends the IP address of a site that is closest to the client.
Note: In the static GSLB database the locations consist of an IP address range and up to six qualifiers for this range.
In order to use static proximity feature you have to upload the database on the appliance. The custom database is stored in ns.conf, and a static third party database or the database of the appliance is stored in the /var/netscaler/locdb directory, by default.
Static Proximity When using a NetScaler Appliance
A client sends a request for a domain to access an application by using resources such as internet, email, or VPN. The client requests for www.example.com by using the browser. The information for this website is stored at two different data centers, Site A and Site B. If the IP address for the domain is not found in the local cache, then the browser sends a request to the client LDNS server.
If the LDNS server does not have an IP address for a requested domain, then it sends a query to a NetScaler appliance that is configured as the authoritative DNS server for the domain.
When the appliance receives the request from the client LDNS, the appliance uses the static database to determine if the IP address and the location information of the client exists.
The appliance then sends the IP address of the nearest data center to the client and the client browser displays the web page.