CIDR index use for '<<' operator

Postgres doesn't seem to make use of indexes when doing operations with the
CIDR '<<' (contains) operator. Is this intended behavior or impossible for
some reason?

test=> \d a
Table "a"
Attribute | Type | Modifier
-----------+------+----------
a | cidr | not null
Index: a_pkey

test=> EXPLAIN SELECT * FROM a WHERE a.a = '192.168.0.128/32'::cidr;
NOTICE: QUERY PLAN:

Index Scan using a_pkey on a (cost=0.00..2.16 rows=1 width=12)

EXPLAIN
test=> EXPLAIN SELECT * FROM a WHERE a.a << '192.168.0.128/30'::cidr;
NOTICE: QUERY PLAN:

Seq Scan on a (cost=0.00..1205.20 rows=32768 width=12)

EXPLAIN
test=>

--
Kendall Koning
Senior Network Engineer, egl.net
Ph: (616) 392-9949 x26