For VRRP, you will want to find the NetworkOS version you currently have installed and review the "Layer 3 Routing Configuration Guide". For a general example the L3 guide for NOS 7.0.1 can be found here:
Athiwat, to my knowledge both NetworkOS and NetIron do not have any feature similar to Cisco's IP SLA. If your concern is turning down a virtual interface in the event the physical interface goes down, you can use VRRP-E tracking to accomplish this. The only caveat is that this feature is not able to track an IP address, only a physical interface.
Michael Morey Principal Technical Support Engineer Extreme Networks