Unable to create shard

[Surender Reddy]

Hi Experts,
  I am trying to create a shard  but failing with the following error.
 
http://35.193.142.167:8081/solr/admin/collections?action=CREATESHARD&collection=external-aggregated&shard=shard-test

{
  "responseHeader":{
    "status":400,
    "QTime":19},
  "Operation createshard caused 
exception:":"org.apache.solr.common.SolrException:org.apache.solr.common.SolrException:
 Cannot create 1 new replicas for collection external-aggregated given the 
current number of live nodes and a maxShardsPerNode of -1",
  "exception":{
    "msg":"Cannot create 1 new replicas for collection external-aggregated 
given the current number of live nodes and a maxShardsPerNode of -1",
    "rspCode":400},
  "error":{
    "metadata":[
      "error-class","org.apache.solr.common.SolrException",
      "root-error-class","org.apache.solr.common.SolrException"],
    "msg":"Cannot create 1 new replicas for collection external-aggregated 
given the current number of live nodes and a maxShardsPerNode of -1",
    "code":400}}

Collection is already defined and core has shards created using the following 
command and already indexed the data.I just want to create a new shard and 
index the data.

/admin/collections?action=CREATE&name=external-aggregated&router.name=implicit&shards=shard-swooptalent,shard-sandisk,shard-smashfly,shard-smashflysales,shard-ge1,shard-ch2m,shard-other&replicationFactor=1&maxShardsPerNode=-1&createNodeSet=EMPTY&collection.configName=external-aggregated

Appreciate any help!

Thanks,
  Surender.