The BSE benchmark index Sensex gained 218 points in early trade today on sustained buying by funds and retailers, amid a firming trend in Asian markets.The 30-share index, which had gained over 741 points in last four trading sessions, shot up by 218 points, or 1.24 per cent, to 17,823 in the opening trade today, with all sectoral indices gaining up to 2.13 per cent.In a similar fashion, the wide-based Nifty of the National Stock Exchange moved up by 60 points, or 1.12 per cent, to 5,385.In Asia, Hong Kong's Hang Seng Index rose by 1.13 per cent and Japan's Nikkei by 1.05 per cent in early trade today. The Dow Jones Industrial Average ended higher by 1.23 per cent on Friday's trade.