Network Router User Manual

Web OS 10.0 Application Guide
Chapter 10: Health Checking
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212777-A, February 2002
Real Server Health Checks
Alteon Web switches running Server Load Balancing (SLB) monitor the servers in the real
server group and the load-balanced application(s) running on them. If a switch detects that a
server or application has failed, it will not direct any new connection requests to that server.
When a service fails, an Alteon Web switch can remove the individual service from the load-
balancing algorithm without affecting other services provided by that server.
By default, the Web switch checks the status of each service on each real server every two sec-
onds. Sometimes, the real server may be too busy processing connections to respond to health
checks. If a service does not respond to four consecutive health checks, the switch, by default,
declares the service unavailable. You can modify both the health check interval and the number
of retries.
NOTE – Health checks are performed sequentially when used in conjunction with a virtual
server configured with multiple services and groups. As a result, the actual health-check inter-
val could vary significantly from the value set for it using the inter parameter.
>> # /cfg/slb/real <real server number> (Select the real server)
>> Real server# inter 4 (Check real server every 4 seconds)
>> Real server# retry 6 (If 6 consecutive health checks fail,
declare real server down)