Network Router User Manual

212777-A, February 2002
219
CHAPTER 10
Health Checking
Content 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 is
distributed 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.
n “Real Server Health Checks” on page 221. This section explains the switch’s default
health check, which checks the status of each service on each real server every two
seconds.
n “DSR Health Checks” on page 222. This section describes the servers’ ability to respond
to the client queries made to the Virtual server IP address when the server is in Direct
Server Return (DSR) mode.
n “Link Health Checks” on page 223. This section describes how to perform Layer 1 health
checking on an Intrusion Detection Server (IDS).
n “TCP Health Checks” on page 224. TCP health checks help verify the TCP applications
that cannot be scripted.
n “ICMP Health Checks” on page 224. This section explains how ICMP health checks are
used for UDP services.
n “Script-Based Health Checks” on page 225. This section describes how to configure the
switch to send a series of health-check requests to real servers or real server groups and
monitor the responses.
n Application-based health checks:
“HTTP Health Checks” on page 231. This section provides examples of HTTP-based
health checks using hostnames.
“UDP-Based DNS Health Checks” on page 233. This section explains the functional-
ity of the DNS Health Checks using UDP packets.