node with dynamic IP

 From: https://devcentral.f5.com/wiki/iRules.resolv__lookup.ashx

 Select the first returned IP address as the destination IP (inherits the destination port from the client's destination port).
when RULE_INIT {
   set static::dns_vs my_dns_vs
}
when CLIENT_ACCEPTED {

    Get IP(s) for hostname www.example.com against 4.2.2.1 name server
   set ips [RESOLV::lookup @$static::dns_vs -a "www.example.com"]

    Log result. If there are multiple IP's it could be a TCL list like {1.1.1.1 2.2.2.2 3.3.3.3}.
   log local0. "Looked up www.example.com and found $ips, parsed first element: [lindex $ips 0]"

    Check if the first list element was empty
   if {$ips eq ""}{
       Input wasn't an IP address, take some default action?
   } else {
       Select the IP 
      node [lindex $ips 0]
   }
}