Can't access VM Ware ESX 3.0 Server from a Diff Subnet

I am running ESX 3.0 and can not access the ESX Server froma diff subnet. I can access the VM just finr from the other subnets. I was told this is a Security setting. How adn wher would I change this?  I can't eve ping the server yet i can the VM's on teh same supbet.