require 'rbvmomi'
credentials = { :host => "192.168.1.10", :user => "administrator@vsphere.local", :password => "vmware", :insecure => true }

vim = RbVmomi::VIM.connect(credentials)
datacenter = vim.rootFolder.childEntity.first      # grab the first datacenter
datacenter.hostFolder.childEntity                  # this will return an array of all the clusters in the datacenter
cluster = datacenter.hostFolder.childEntity.first  # grab the first cluster from the datacenter
cluster.host                                       # this will return an array of all the ESXi hosts in the first cluster
host = cluster.host.first                          # grab the first host in the cluster
host.config.network.vnic                           # display all the vnics on the host
host.config.network.vnic.first.spec.ip.ipAddress   # display the ip address bound the to first vnic on the host