It took me a while to understand the help for the configuration file for HAProxy, another software load balancer that runs on a number of *nix-based systems. Here’s the resulting file that we used to successfully test an active-passive machine configuration that someone will hopefully find useful one day.
global
log 127.0.0.1 alert
log 127.0.0.1 alert debug
maxconn 4096
defaults
log global
mode http
option httplog
option dontlognull
option redispatch
retries 3
maxconn 2000
contimeout 5000
clitimeout 50000
srvtimeout 50000
####################################
#
# loadbalancer
# 10.0.16.222:8555
# / \
# webServerA webServerB
# 10.0.5.91:8181 10.0.5.92:8181
# (active) (passive)
#
####################################
listen webfarm 10.0.16.222:8555
mode http
stats enable
balance roundrobin
option httpclose
option forwardfor
option httplog
option httpchk GET /someService/isAlive
server webServerA 10.0.5.91:8181 check inter 5000 downinter 500 # active node
server webServerB 10.0.5.92:8181 check inter 5000 backup # passive node
