Failed to setup ES cluster on EC2

The first cluster start up as master successfully. (ip: 10.28.99.235)

But second ES instance cannot join first one.

Here is the elasticsearch.yml
cluster.name: xxx
Cloud:
aws:
access_key: xxx
secret_key: xxx
region: us-east-1
bootstrap.mlockall: true
network:
bind_host: eth0:ipv4
gateway:
type: s3
s3:
bucket: xxx
discovery:
type: ec2
ec2:
ping_timeout: 5s

And here is some of log:

[INFO ][node ] [Ricadonna] {0.19.9}[5135]: initializing
...
[2012-08-27 10:24:19,627][INFO ][plugins ] [Ricadonna]
loaded [cloud-aws], sites []
[2012-08-27 10:24:21,168][DEBUG][discovery.zen.ping.multicast] [Ricadonna]
using group [224.2.2.4], with port [54328], ttl [3], and address [null]
[2012-08-27 10:24:21,171][DEBUG][discovery.zen.ping.unicast] [Ricadonna]
using initial hosts [], with concurrent_connects [10]
[2012-08-27 10:24:21,172][DEBUG][discovery.ec2 ] [Ricadonna]
using ping.timeout [5m], master_election.filter_client [true],
master_election.filter_data [false]
[2012-08-27 10:24:21,176][DEBUG][discovery.zen.elect ] [Ricadonna]
using minimum_master_nodes [-1]
[2012-08-27 10:24:21,177][DEBUG][discovery.zen.fd ] [Ricadonna]
[master] uses ping_interval [1s], ping_timeout [30s], ping_retries [3]
[2012-08-27 10:24:21,180][DEBUG][discovery.zen.fd ] [Ricadonna]
[node ] uses ping_interval [1s], ping_timeout [30s], ping_retries [3]
[2012-08-27 10:24:21,434][DEBUG][discovery.ec2 ] [Ricadonna]
using host_type [PRIVATE_IP], tags [{}], groups [[]] with any_group [true],
availability_zones [[]]
[2012-08-27 10:24:22,591][DEBUG][gateway.s3 ] [Ricadonna]
using bucket [autodesk-es-storage-staging], region [null], chunk_size
[100mb], concurrent_streams [5]
[2012-08-27 10:24:23,828][DEBUG][gateway.s3 ] [Ricadonna]
Latest metadata found at index [58]
[2012-08-27 10:24:23,831][INFO ][node ] [Ricadonna]
{0.19.9}[5135]: initialized
[2012-08-27 10:24:23,831][INFO ][node ] [Ricadonna]
{0.19.9}[5135]: starting ...
[2012-08-27 10:24:23,982][INFO ][transport ] [Ricadonna]
bound_address {inet[/10.215.82.16:9300]}, publish_address
{inet[/10.215.82.16:9300]}
[2012-08-27 10:24:23,998][TRACE][discovery ] [Ricadonna]
waiting for 30s for the initial state to be set by the discovery
[2012-08-27 10:24:24,972][TRACE][discovery.ec2 ] [Ricadonna]
building dynamic unicast discovery nodes...
[2012-08-27 10:24:24,983][TRACE][discovery.ec2 ] [Ricadonna]
adding i-e741e58c, address 10.192.207.132, transport_address
inet[/10.192.207.132:9300]
[2012-08-27 10:24:24,985][TRACE][discovery.ec2 ] [Ricadonna]
adding i-53033538, address 10.210.230.15, transport_address
inet[/10.210.230.15:9300]
[2012-08-27 10:24:24,991][TRACE][discovery.ec2 ] [Ricadonna]
adding i-d4c7cdbf, address 10.193.134.63, transport_address
inet[/10.193.134.63:9300]
[2012-08-27 10:24:24,997][TRACE][discovery.ec2 ] [Ricadonna]
adding i-eed6dc85, address 10.211.7.162, transport_address
inet[/10.211.7.162:9300]
(many many adding....98 addings in total)
[2012-08-27 10:24:25,267][DEBUG][discovery.ec2 ] [Ricadonna]
using dynamic discovery nodes
[[#cloud-i-e741e58c-0][inet[/10.192.207.132:9300]],
[#cloud-i-53033538-0][inet[/10.210.230.15:9300]],
[#cloud-i-d4c7cdbf-0][inet[/10.193.134.63:9300]],
[#cloud-i-eed6dc85-0][inet[/10.211.7.162:9300]],
[#cloud-i-ecd6dc87-0][inet[/10.210.77.161:9300]],
[#cloud-i-79489f13-0][inet[/10.211.87.79:9300]],
[#cloud-i-7faa7c15-0][inet[/10.208.70.31:9300]],
[#cloud-i-9e6ac5f4-0][inet[/10.208.146.96:9300]],
[#cloud-i-161ba27c-0][inet[/10.217.67.175:9300]],
[#cloud-i-9a4bf7f7-0][inet[/10.104.91.252:9300]],
[#cloud-i-142c9079-0][inet[/10.198.139.202:9300]],
[#cloud-i-52fa983f-0][inet[/10.208.71.0:9300]],
[#cloud-i-807e5ded-0][inet[/10.198.131.185:9300]],
[#cloud-i-036df16f-0][inet[/10.96.226.193:9300]],
[#cloud-i-971119fb-0][inet[/10.203.29.185:9300]],
[#cloud-i-911119fd-0][inet[/10.116.115.159:9300]],
[#cloud-i-912d25fd-0][inet[/10.203.33.229:9300]],
[#cloud-i-aba1a9c7-0][inet[/10.118.250.13:9300]],
[#cloud-i-9f5952f3-0][inet[/10.196.63.128:9300]],
[#cloud-i-967d36f9-0][inet[/10.86.129.154:9300]],
[#cloud-i-bec99ed1-0][inet[/10.195.178.95:9300]],
[#cloud-i-60d6e60f-0][inet[/10.64.18.80:9300]],
[#cloud-i-cd11f4a3-0][inet[/10.64.62.211:9300]],
[#cloud-i-93b947fd-0][inet[/10.104.39.240:9300]],
[#cloud-i-1b3e6b7a-0][inet[/10.110.229.172:9300]],
[#cloud-i-1d3e6b7c-0][inet[/10.254.69.171:9300]],
[#cloud-i-78b85c18-0][inet[/10.2.13.113:9300]],
[#cloud-i-04778764-0][inet[/10.217.9.188:9300]],
[#cloud-i-7659a916-0][inet[/10.70.249.34:9300]],
[#cloud-i-485aaa28-0][inet[/10.210.202.179:9300]],
[#cloud-i-2626da46-0][inet[/10.111.18.102:9300]],
[#cloud-i-0e2ed06e-0][inet[/10.104.123.200:9300]],
[#cloud-i-102ed070-0][inet[/10.47.18.146:9300]],
[#cloud-i-bc5917dc-0][inet[/10.96.119.120:9300]],
[#cloud-i-be5917de-0][inet[/10.73.25.64:9300]],
[#cloud-i-7c39231c-0][inet[/10.2.115.14:9300]],
[#cloud-i-a3de1fc0-0][inet[/10.46.138.152:9300]],
[#cloud-i-d12c91b2-0][inet[/10.46.213.163:9300]],
[#cloud-i-bf8837dc-0][inet[/10.46.37.71:9300]],
[#cloud-i-bd8837de-0][inet[/10.96.193.40:9300]],
[#cloud-i-f95cdb9a-0][inet[/10.96.147.146:9300]],
[#cloud-i-f902459a-0][inet[/10.110.247.177:9300]],
[#cloud-i-fdbe9f9e-0][inet[/10.83.95.21:9300]],
[#cloud-i-488e792a-0][inet[/10.211.71.135:9300]],
[#cloud-i-88fe09ea-0][inet[/10.241.107.15:9300]],
[#cloud-i-cee215ac-0][inet[/10.198.109.139:9300]],
[#cloud-i-cee116ac-0][inet[/10.73.70.89:9300]],
[#cloud-i-b2e116d0-0][inet[/10.68.203.72:9300]],
[#cloud-i-74ef1816-0][inet[/10.211.93.124:9300]],
[#cloud-i-04e81f66-0][inet[/10.3.26.98:9300]],
[#cloud-i-dcd225be-0][inet[/10.201.183.31:9300]],
[#cloud-i-20d12642-0][inet[/10.66.147.115:9300]],
[#cloud-i-48c7302a-0][inet[/10.46.147.216:9300]],
[#cloud-i-f2c53290-0][inet[/10.96.85.250:9300]],
[#cloud-i-8ccd3aee-0][inet[/10.188.2.83:9300]],
[#cloud-i-7ecb3c1c-0][inet[/10.71.21.190:9300]],
[#cloud-i-a2cb3cc0-0][inet[/10.190.218.232:9300]],
[#cloud-i-8439cee6-0][inet[/10.68.215.208:9300]],
[#cloud-i-8a2ddae8-0][inet[/10.240.59.64:9300]],
[#cloud-i-1dd13278-0][inet[/10.76.7.62:9300]],
[#cloud-i-cb4fc6ae-0][inet[/10.210.71.224:9300]],
[#cloud-i-3b22ab5e-0][inet[/10.215.13.204:9300]],
[#cloud-i-1f44dd7a-0][inet[/10.211.7.112:9300]],
[#cloud-i-e7a1e682-0][inet[/10.4.207.61:9300]],
[#cloud-i-89afe8ec-0][inet[/10.64.137.165:9300]],
[#cloud-i-0dadea68-0][inet[/10.189.7.155:9300]],
[#cloud-i-5abaec3f-0][inet[/10.108.70.164:9300]],
[#cloud-i-64aeff01-0][inet[/10.71.27.190:9300]],
[#cloud-i-081a4a6d-0][inet[/10.188.113.156:9300]],
[#cloud-i-dc1b4bb9-0][inet[/10.104.113.55:9300]],
[#cloud-i-4c346429-0][inet[/10.68.139.176:9300]],
[#cloud-i-56366633-0][inet[/10.6.150.242:9300]],
[#cloud-i-8ddb2ee9-0][inet[/10.28.70.41:9300]],
[#cloud-i-59c5303d-0][inet[/10.28.70.30:9300]],
[#cloud-i-f1c53095-0][inet[/10.28.65.5:9300]],
[#cloud-i-1dfc6879-0][inet[/10.110.231.162:9300]],
[#cloud-i-794d3d1d-0][inet[/10.28.38.50:9300]],
[#cloud-i-d1017ab5-0][inet[/10.28.69.87:9300]],
[#cloud-i-af047fcb-0][inet[/10.28.100.82:9300]],
[#cloud-i-41eb3127-0][inet[/10.218.103.151:9300]],
[#cloud-i-91aadbf7-0][inet[/10.111.29.128:9300]],
[#cloud-i-9de392fb-0][inet[/10.28.150.160:9300]],
[#cloud-i-ffd5f499-0][inet[/10.28.139.205:9300]],
[#cloud-i-775a7a11-0][inet[/10.68.6.132:9300]],
[#cloud-i-6b38180d-0][inet[/10.28.78.231:9300]],
[#cloud-i-fadc1e83-0][inet[/10.191.87.30:9300]],
[#cloud-i-6a9cee13-0][inet[/10.64.30.59:9300]],
[#cloud-i-1248346b-0][inet[/10.64.77.95:9300]],
[#cloud-i-aaec90d3-0][inet[/10.195.194.3:9300]],
[#cloud-i-eedd8e97-0][inet[/10.210.10.194:9300]],
[#cloud-i-a0ec1ed8-0][inet[/10.220.31.77:9300]],
[#cloud-i-13519f68-0][inet[/10.146.144.185:9300]],
[#cloud-i-e367bf98-0][inet[/10.146.144.187:9300]],
[#cloud-i-739b4008-0][inet[/10.146.144.219:9300]],
[#cloud-i-cdc962b6-0][inet[/10.110.89.24:9300]],
[#cloud-i-c3c962b8-0][inet[/10.2.9.145:9300]],
[#cloud-i-27ca515c-0][inet[/10.215.82.16:9300]],
[#cloud-i-a70e64dc-0][inet[/10.28.99.235:9300]]]

I tried to set zen ping timeout to a large value, but it doesn't work. The
adding and connecting part seems appear again and again.

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