def manager(&lam)
  SNMP::Manager.open(@manager_config, &lam)
end

def walk_table(table, &block)
  manager do |m|
    m.walk(table) { |row| yield row.collect{ |vb| vb.value.to_s } }
  end
end

def get_mac(vlan_index, ip_address)
  manager do |m|
    m.get_value("ipNetToMediaPhysAddress.#{vlan_index}.#{ip_address}")
  end
end