212777-A, February 2002 219CHAPTER 10Health CheckingContent intelligent Web switches allow Web masters to customize server health checks to ver-ify content accessibility in large Web sites. As the amount of content grows and information isdistributed across different server farms, flexible, customizable content health checks are criti-cal to ensure end-to-end availability.The following Web OS health-checking topics are described in this chapter. “Real Server Health Checks” on page 221. This section explains the switch’s defaulthealth check, which checks the status of each service on each real server every twoseconds. “DSR Health Checks” on page 222. This section describes the servers’ ability to respondto the client queries made to the Virtual server IP address when the server is in DirectServer Return (DSR) mode. “Link Health Checks” on page 223. This section describes how to perform Layer 1 healthchecking on an Intrusion Detection Server (IDS). “TCP Health Checks” on page 224. TCP health checks help verify the TCP applicationsthat cannot be scripted. “ICMP Health Checks” on page 224. This section explains how ICMP health checks areused for UDP services. “Script-Based Health Checks” on page 225. This section describes how to configure theswitch to send a series of health-check requests to real servers or real server groups andmonitor the responses. Application-based health checks:o “HTTP Health Checks” on page 231. This section provides examples of HTTP-basedhealth checks using hostnames.o “UDP-Based DNS Health Checks” on page 233. This section explains the functional-ity of the DNS Health Checks using UDP packets.
