SSH to ela throwing error "Too many authentication failures"

Problem

You may encounter the issue below while connecting to the front end Ela with the command ssh -A ela.cscs.ch:

Received disconnect from UNKNOWN port 65535:2: Too many authentication failures

You may have too many keys in your ssh agent. You should remove the unused keys with the following command:

ssh-add -d name-of-the-key-to-be-removed #Example: ssh-add -d cscs-key  
ssh-add -D                               #To remove all keys