Question about a CIDR based query

Hello,

Consider that I have the following table:

Create Table tmp(
            route_id     int    NOT NULL,
            route         cidr   NOT NULL,
            Data         varchar(100) NOT NULL)

The table contains ~40,000 routes and I have an index on route.

The query I am interested in is:

select * from tmp where route >>= some_cidr

The index on route is not used and I get a sequential scan. The index is 
used only for the <<= operator.

Any idea how I can make  the query run faster?

Thanks,
George