ES embedded nodes in different data center

We are using ES 1.5 as embedded data node within our
product. The reason is so that we can ship and do deployment using a single
package. Within in same cluster we can
configure unicast by mentioning the hosts IP addresses. But if we deploy the ES node to two clusters and
these clusters are in different data centers then what is the best and possible
option for them to communicate and join a one Elastic Search Cluster?

Thanks
Dav

We do not recommend this as the links between DCs cannot be guaranteed to be reliable enough to maintain a healthy cluster.