The LoadMaster utilizes health checks to monitor the availability of the Real Servers and the Virtual Services. If one of the servers does not respond to a health check within a defined time interval for a defined number of times, the weighting of this server will be reduced to zero. This zero weighting has the effect of removing the Real Server from the Virtual Service configuration until it can be determined that this Real Server is back online. The LoadMaster uses health checks that can be specified in the WUI. By default, the highest possible health check is associated with a Virtual Service. The LoadMaster performs Layer 7 health checks for the following ports:

Service

Port

Protocol

FTP

21

TCP

TELNET

23

TCP

SMTP

25

TCP

HTTP

80

TCP

HTTPS

443

TCP

POP3

110

TCP

NNTP

119

TCP

IMAP

143

TCP

DNS

53

UDP

LDAP

389/636

UDP/TCP
Note: When creating a Virtual Service and using a service type other than Generic, additional health checking protocols are available. For example, the service type Remote Terminal will permit checking with Remote Terminal Protocol.
Note: The Remote Terminal Protocol supports Network Level Authentication.

For other ports the LoadMaster uses Layer 4 health checks for TCP services and Layer 3 health checks for UDP services. The settings for the health checks can be changed from the default settings using the Virtual Service wizard to accommodate non-standard settings. For example, one could run an http service on port 8080 instead of 80, and change the health check to HTTP instead of the default Layer 4 check.

Note: These global settings hold for all servers in the farm, that is, you cannot assign different timeouts for different servers.

It is mandatory that one of the service checking options be used when defining a Virtual Service on the LoadMaster.