Elasticsearch returns exception master not discovered

[alexus]

[root@7pvelk02 ~]# curl --silent $(hostname):9200/_cat/indices?pretty
{
  "error" : {
    "root_cause" : [
      {
        "type" : "master_not_discovered_exception",
        "reason" : null
      }
    ],
    "type" : "master_not_discovered_exception",
    "reason" : null
  },
  "status" : 503
}
[root@7pvelk02 ~]# 

/var/log/elasticsearch/X.log:

[2017-06-22T15:46:38,850][INFO ][o.e.d.z.ZenDiscovery ] [7pvelk02] failed to send join request to master [{7pvelk01}{2OLRVS4iRqi7TeO3reYmog}{2M8IRM3MS3CxuzoAwszxIA}{10.52.223.137}{10.52.223.137:9300}], reason [RemoteTransportException[[7pvelk01][10.52.223.137:9300][internal:discovery/zen/join]]; nested: ConnectTransportException[[7pvelk02][10.52.223.237:9300] connect_timeout[30s]]; nested: IOException[No route to host: 10.52.223.237/10.52.223.237:9300]; nested: IOException[No route to host]; ]

nmap (network):

[root@7pvelk02 ~]# nmap -p 9200,9300 7pvelk01  | grep open
9200/tcp open  wap-wsp
9300/tcp open  vrace
[root@7pvelk02 ~]# 

Please advise.