Nortel Networks WEB OS 212777 - Manual (Page 221)

Web OS 10.0 Application Guide
Chapter 10: Health Checking n 221
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.
N OTE – 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)