IRule monitor node status

Hi all

 

I a new F5 , pls help me check a irule bellow , i want monitor status of node 1.2.3.4 , at the time , it not work .

 

 

when RULE_INIT {

 

set static::whitelist_ttl "300"

 

}

 

when DNS_REQUEST {

 

set fqdn [DNS::question name]

 

.....

 

if { [ class match [ LB::status node 1.2.3.4 ] eq "up " ] }

 

{

 

....

 

}

 

 

}

 

pls help me

 

many thanks