How to configure mysql group replication with different ports?

I have a k8s cluster and each mysql instance is well connected together! But I have another mysql server outside the cluster! Each mysql inside the cluster has a default mysql port, which is 3306 and an external port; which is something random! So when I start mysql group replication with the instances that are inside the cluster everything works fine! the thing is the mysql instance that is outside of the cluster is trying to connect to the 3306 default port with repl user but it should be connecting to the random port generated! and I don't know how to specify it to connect to the port I want to connect... **how can i specify the outsider instance to use that random generated port to connect to other instances inside the cluster to use mysql group replication?** here is my error log:

error connecting to master 'repl@db1-headless:3306'