3-22 T-Series Traffic Director Installation, Configuration and Administration Guide
Chapter 3 Basic T1000/Unison Load-Balancing Configuration
Configuring Health Checks and Redundancy
Once load balancing is configured, the T1000s require additional configurations to monitor
the health of the OSNs, to define a minimum operating threshold, and to specify the T1000
failover behavior for redundancy.
• “Configuring Health Monitors” on page 3-22
• “Configuring Minimum Servers and Backup Path” on page 3-24
• “Configuring Failover Redundancy” on page 3-24
• “Configuring Route Monitors in HA Mode” on page 3-25
Configuring Health Monitors
The T1000 provides health monitors to verify the proper operation of OSN servers. A health
monitor typically tests a device for an expected response within a specified time interval and
marks it as unhealthy in case of a failure. The sample configuration defines an HTTP health
check at port 5100 with these options:
• The health check is performed every 5 seconds.
• Three consecutive failed health check attempts are required before declaring a
previously healthy server as inoperative
• One consecutive successful health check attempts are required before declaring a
previously inoperative server as healthy
• The duration for which the system waits to make the next probe once the service is
marked as down is 30 seconds.
The add lb monitor has the following syntax for this purpose.
add lb monitor monitorName type [-respCode int[-int] ...] [-httpRequest string]
[-LRTM {ENABLED | DISABLED}] [-destIP ip_addr] [-destPort port]
For example, to add the health monitor to the ingress ports of all the OSNs in the sample
configuration (Unison Release 6.0 or higher only
1
):
>add lb monitor "Watchdog Port 5100" HTTP -respCode 200 -httpRequest "HEAD /"
-LRTM ENABLED -destPort 5100
Done
Another less typical example is the requirement for a passthrough monitor that can verify
the L3 health of both the ingress and egress interfaces of an OSN:
> add lb monitor passthrough-icmp PING -LRTM DISABLED -destIP 169.254.64.100
-transparent YES
Done
1. For Unison releases prior to 6.0, HTTP Request "GET /\r\nJunk:" must be used in place of
"HEAD /". This workaround is required because T1000 appends HTTP/1.0 onto the string,
causing the watchdog process to always return 200.
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