F5GTM中健康检查

如图所示，GTM gateway_icmp健康检查中的几个参数解释

1. Interval：Specifies, in seconds, the frequency at which the system issues the monitor check when either the resource is down or the status of the resource is unknown. The default is 30.
2. Timeout：Displays the number of seconds the target has in which to respond to the monitor request. The default is 120 seconds. If the target responds within the set time period, it is considered up. If the target does not respond within the set time period, it is considered down. When this value is set to 0 (zero), the system uses the interval from the parent monitor. Note that Timeout and Time Until Up combine to control when a resource is set to up.
3. Probe Interval：Displays the number of seconds the big3d process waits before sending out a subsequent probe attempt when a probe fails and multiple probe attempts have been requested. The default is 1
4. Probe Timeout：Displays the number of seconds after which the system times out the probe request to the system. The default value is 5.
5. Probe Attempts：Displays the number of times the system attempts to probe the host server, after which the system considers the host server down or unavailable. The default value is 3

上图：关闭Server
在10:40:56发送icmp没有回复，每秒又发送了一次（Probe Interval=1秒），发送了3次（Probe Attempts=3），当达到Probe Timeout （5秒），标记为down
在/var/log/gtm中显示10:41:01,即5秒后显示：“Jul 11 10:41:01 BIGIPActive alert gtmd[5770]: 011a5004:1: SNMP_TRAP: Server /Common/Server_test (ip=10.128.10.120) state change green --> red (No enabled VS available)”

接下来的探测抓包