No default realm defined for Kerberos

When you connect to some old cisco routers using iterm2 on an OS X, it might takes some time before it prompts for a username. And it might also promt you with this message.

Kerberos: No default realm defined for Kerberos! 

To disable this message you need to create or edit the file .telnetrc in your home directory and add default unset autologin

$ vim ~/.telnetrc
  default unset autologin

esc : wq