You can use openconnect to connect to a Juniper VPN:
openconnect --juniper mivpn.es
It will parse the web and will ask you for user/password.
But sometimes this does not work, so you would have to login via web and then copy the cookie DSID:
openconnect --juniper -C "DSID=ab353bbbcd677e8adf5a2f335b6c77ac" mivpn.es