cqlsh query on secondary indexed column rpc timeout - timeout

Question

I am finding trouble in why my query in secondary indexed column in cassandra getting rpc timeout.
Here is my details about the cassandra and table
[cqlsh 4.1.1 | Cassandra 2.0.7 | CQL spec 3.1.1 | Thrift protocol 19.39.0]
cqlsh:master_hub_development> describe table service_hubs;
CREATE TABLE service_hubs (
id uuid,
host text,
hub_name text,
os text,
owner text,
pubkey text,
service_type text,
trust int,
PRIMARY KEY (id)
) WITH
bloom_filter_fp_chance=0.010000 AND
caching='KEYS_ONLY' AND
comment='' AND
dclocal_read_repair_chance=0.000000 AND
gc_grace_seconds=864000 AND
index_interval=128 AND
read_repair_chance=0.100000 AND
replicate_on_write='true' AND
populate_io_cache_on_flush='false' AND
default_time_to_live=0 AND
speculative_retry='99.0PERCENTILE' AND
memtable_flush_period_in_ms=0 AND
compaction={'class': 'SizeTieredCompactionStrategy'} AND
compression={'sstable_compression': 'LZ4Compressor'};
CREATE INDEX service_hubs_host_idx ON service_hubs (host);
CREATE INDEX service_hubs_hub_name_idx ON service_hubs (hub_name);
CREATE INDEX service_hubs_os_idx ON service_hubs (os);
CREATE INDEX service_hubs_owner_idx ON service_hubs (owner);
CREATE INDEX service_hubs_pubkey_idx ON service_hubs (pubkey);
CREATE INDEX service_hubs_service_type_idx ON service_hubs (service_type);
CREATE INDEX service_hubs_trust_idx ON service_hubs (trust);
cqlsh:master_hub_development> select * from service_hubs;
id | host | hub_name | os | owner | pubkey | service_type | trust
--------------------------------------+----------------+--------------------+--------+---------------+--------+--------------+-------
b9d9bd06-e006-11e3-a1e2-3382b7d578d2 | localhost:3001 | HUB:Darknetdb | Mac os | darknet_admin | null | darknetdb | 90
b9d74918-e006-11e3-a1e2-3382b7d578d2 | localhost:3000 | HUB:Darknetbitcoin | Mac os | darknet_admin | null | bitcoin | 90
b9da9b2c-e006-11e3-a1e2-3382b7d578d2 | localhost:3002 | HUB:Darknetemail | Mac os | darknet_admin | null | email | 90
b9db8596-e006-11e3-a1e2-3382b7d578d2 | localhost:3003 | HUB:Darknetftp | Mac os | darknet_admin | null | ftp | 90
(4 rows)
cqlsh:master_hub_development> select * from service_hubs where host='localhost:3001';
id | host | hub_name | os | owner | pubkey | service_type | trust
--------------------------------------+----------------+---------------+--------+---------------+--------+--------------+-------
b9d9bd06-e006-11e3-a1e2-3382b7d578d2 | localhost:3001 | HUB:Darknetdb | Mac os | darknet_admin | null | darknetdb | 90
(1 rows)
cqlsh:master_hub_development> select * from service_hubs where service_type='darknetdb';
Request did not complete within rpc_timeout.
Here we can see that the query on secondary index column host gets succeeded but the similar query on service_type gets rpc_timeout error.
I am not able to find the reason behind it why it rpc_timeouted in this query.
select * from service_hubs where service_type='darknetdb';
Thanks