index-match between two huge files

Hi All , i need help , i have two sheets each one with almost 800,000 rows and i need to vlookup value from one sheet and fill it in the other sheet , i tried bioth vlookup and index-match and both keep PC hang for ever and very very slow 9almost not in service).

i attached two sheets (with sample small number of rows ) , need how to fill in VLAN column in the (allports-test sheet) using data from the other sheet (VLAN-Test sheet) , remember that sheet shall contain 800 thousand rows so you can complete the sheets (due to file size i cant send full sheeet).

thanks for your quick response,

i am using Excel 2007 and i didnt find Blookup function , is there any other solution ? macro or function to do the job ? Thanks in advance.