Chapter 12. Exploring Global Server Load Balancing

Chapter Goals

In this Chapter, you will learn how to configure Global Server Load Balancing (GSLB). The Chapter is divided into the following sections:

• Introducing the Domain Name Service (DNS)You will learn about DNS resource records and iterative and recursive DNS.

• Exploring Distributed Director (DD) TechnologiesYou will learn how to configure the DD to distribute client traffic across multiple sites.

• Exploring Content Services Switch (CSS) GSLBYou will learn how to configure the CSS to distribute client requests across multiple sites.

• Exploring Cisco Service Switching Module (CSM) GSLBYou will learn how to configure the CSM to distribute client requests across multiple sites.

• GSLB StickinessYou will learn about stateless DNS sticky (with source IP address hashing) and stateful DNS-sticky using a Global Sticky Database (GSDB).

In this Chapter, you will learn how to resolve issues relating to disaster recovery, name resolution response times increases, and data center capacity increases. By mirroring your content across geographically distributed data centers and enabling the Global Server Load Balancing (GSLB) intelligent request routing capabilities discussed in this Chapter, you can resolve many present and future redundancy, response time, and scalability issues.

You will learn about the following GSLB technologies in this Chapter:

• DNS Round-Robin Distributes requests across sites using round-robin with DNS servers only[md]no GSLB devices are required.

• BGP anycast Advertises the site prefix from multiple locations into BGP; routers automatically distribute requests to the prefix based on BGP attributes, such as AS path.

• DNS GSLB Distributes requests based on various metrics, such as proximity, and stickiness, across sites using GSLB devices enabled with DNS capabilities.

• HTTP Redirection Distributes client requests across sites using the HTTP 301 Moved redirection method.

• Route Health Injection Advertises host routes for healthy VIPs into the routing table, and routers select the VIP with the best routing metric for client requests.

You can enable one or more of these technologies in your network to achieve GSLB.