Cassandra communication failure between Seed <->Non-seed

Hello,
Just a beginner on Rancher.

My problem on Rancher is communication failure between Seed <->Non-seed,
The reason is ‘link:’ doesn’t work well as I expected.

Example
cass1:
hostname:cass1
image:035824440926.dkr.ecr.us-east-1.amazonaws.com/aircel/cassandra224:1.11
links:

  • cass2:cass2

cass2:
hostname:cass2
image:035824440926.dkr.ecr.us-east-1.amazonaws.com/aircel/cassandra224:1.11
links:

  • cass1:cass1

In /etc/host of cass1
172.17.0.5 cass1 <-- this is ok, expected by hostname:
127.0.0.1 localhost
172.17.0.6 cass2 <-- expecting this by link: , but not exist

In /etc/host of cass2
172.17.0.6 cass2 <— this is ok, expected by hostname:
127.0.0.1 localhost
172.17.0.5 cass1 <— expecting this by link: , but not exist

So, cass1 and cass2 doesn’t know to each other.
Would you share your idea how to make cass1 and cass2 knows each other?

The DNS information is populated using the Rancher IP address. There are metadata and DNS helper services running inside the Network Agent container. Hence /etc/hosts file is not populated as you would expect.

Thanks a lot for your response.
but not sure how 2 nodes know to each other through meta data and DNS helper.
Would you share any link or doc or example (docker-compose.yml) ?

http://docs.rancher.com/rancher/latest/en/rancher-services/internal-dns-service/