Mysql RDS migration problem I'm trying to migrate my MySQL RDS to a different machine. The reason is that I need smaller disk, and you can't make disks smaller for RDS servers, only bigger. 

I'm trying to migrate with this answer:
https://stackoverflow.com/questions/20638012/backup-mysql-amazon-rds#20645291
and this tutorial:
http://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/MySQL.Procedural.Importing.NonRDSRepl.html#MySQL.Procedural.Importing.Start.Repl

Briefly :


Created replica and stopped 
Migrated from replica to a new server
Created user on Source DB with:

CREATE USER 'repl_user'@'%' IDENTIFIED BY 'slavepass';

GRANT REPLICATION SLAVE ON *.* TO 'repl'@'%'
I've pointed to master from slave with this command: 

CALL mysql.rds_set_external_master ('source.mydomain.com', 3306,'repl_user', 'slavepass', 'mysql-bin-changelog.000001', 107, 0);
I've started replication with :

CALL mysql.rds_start_replication;


When checking status with SHOW SLAVE STATUS, it shows that slave can't connect to master.
All servers are in the same security group. I was trying to connect to source with repl_user with MySQL command line and it worked. 
I have no idea where to look next. I think it might be something with security in aws, but I was comparing new server with existing replicas and all seems the same.

I'm running MySQL 5.6 on both machines.
I've managed to make it work with pointing slave to master IP instead of url, and putting slave ip to inbound rules of Master's security group