The CBOE Volatility Index advanced 1.54 points to 17.11 on Wednesday, marking its highest level in two weeks and signaling increased demand for options protection. The move in volatility coincided with a sharp downturn in the equities market, as the S&P 500 slipped below the 6,400 level and briefly touched 6,360— the lower bound of traders’ expected weekly range — after a swift 30-point drop. Option strategists noted that dealers often defend these levels, suggesting potential for a near-term bounce.