Does yum work ? How you installed browser on CentOS 6.5 instance ?
Can you run ?
# curl http://169.254.169.254
# curl http://lxer.com

Hi dbaxps, it shows curl: (7) couldn't connect to the host when I run curl command. There's no 169.254.0.0 route shown in the instance. The instance did not get the ip address from the DHCP server, maybe that's the reason. However, I created the centos qcow2 image following the instructions on openstack website step by step. But I still fail to make things work perfectly.

What says :-
$neutron agent-list

Oh, nothing shown when running this command.

Should look like

   [root@icehouse1 ~(keystone_admin)]# neutron agent-list
    +--------------------------------------+--------------------+-----------------------+-------+----------------+
    | id                                   | agent_type         | host                  | alive | admin_state_up |
    +--------------------------------------+--------------------+-----------------------+-------+----------------+
    | 1dfff64b-2950-4cb4-b275-889f9e19685e | DHCP agent         | icehouse1.localdomain | :-)   | True           |
    | 5d3f04cf-74f7-466c-bd6c-328d73963953 | L3 agent           | icehouse1.localdomain | :-)   | True           |
    | cc96a2d9-4f5b-4298-8ea0-cbab43c002e7 | Open vSwitch agent | icehouse2.localdomain | :-)   | True           |
    | d92d471b-7a06-4184-91d2-a418f7a80a3f | Metadata agent     | icehouse1.localdomain | :-)   | True           |
    | e21de8df-810b-495b-b3a9-a3508c68a171 | Open vSwitch agent | icehouse1.localdomain | :-)   | True           |
    +--------------------------------------+--------------------+-----------------------+-------+------------