Cannot add nodes to my rke cluster

Rancher 2.x
1

I got a functional 2 nodes cluster. I provide two more VM as new nodes and when i try to add this VM as nodes by modifying the cluster.yml with unique role: worker for each of them the cluster failed with some error like this

WARN[0005] Can’t start Docker container [rke-cp-port-listener] on host [IP-OF-MASTER-NODE]: Error response from daemon: driver failed programming external connectivity on endpoint rke-cp-port-listener (3bc8826acc2b247a57a1ed12bfa5a106255d41298440b6c2c93b34c687c7ffa1): Error starting userland proxy: listen tcp 0.0.0.0:6443: bind: address already in use

2

Another process is bound to port TCP/6443 on the new node.

use ‘ss’ or ‘netstat’ to find it.

ss -l4n
or
netstat -l4n