I have a dataset similar to the example below, where the index number is always the same for when Var 1 = Var 2 and Var 2 = Var 1.

What command do I give Stata to drop ONLY the observations when index 1 AND index 2 are identical?
Var 1 Var 2 index 1 index 2
101 202 0.888 0.777
202 101 0.888 0.777
202 333 0.984 0.552
303 404 0.666 0.774
404 303 0.666 0.774