Important Note: The i4 server is no longer accepting requests for new accounts and active websites must be migrated before the scheduled retirement in July 2022.

Before reviewing these troubleshooting steps, please make sure you've completed multi-factor authentication when establishing a connection to the i4 server. If you fail to authenticate before your connection times out, you will receive an error message. Please note that SSH and SFTP clients may have a varying time-out windows.

Need Help?

Connection Issues


If you have difficulty connecting to the server using Dreamweaver, you may need to clear any saved i4 host keys (in a file called ssh_hosts) from your program.

Please note, NYU IT does not distribute or support Dreamweaver, and the NYU Web Team does not provide configuration instructions to access You may wish to consult Adobe's Help Documentation.

Fetch (for version 5.3.1)

  1. Launch Fetch.
  2. In Fetch, choose Fetch Help from the Help menu.
  3. In the help window, search for known hosts.
  4. Double-click on the RSA host key differs warning help topic (it should be the one at the top of the list).
  5. A help topic opens in the help window.
  6. Scroll down to the Delete the known_hosts file for me link. A pop-up window will appear indicating:
    This script will move your .ssh/known_hosts file to the Trash, removing all SSH keys. Are you sure you want to continue?
  7. Click the Yes button.

Once that's done, try connecting to using SFTP again. If you're warned that "the authenticity of the host can't be established" (you may or may not be), that is normal and you should continue.


  1. Launch Fugu.
  2. From the Fugu menu, select the option for Preferences.
  3. Click the icon/option for Known Hosts.
  4. Highlight all instances of
  5. Click the Delete button. Then, click the Save button.
  6. Close that window and quit out of Fugu.
  7. Relaunch the application and try logging in again. You'll probably receive a warning that says:
    The authenticity of host ' (' can't be established. Unable to get host key. Something is odd. Are you sure you want to continue connecting?
  8. Click the Continue button.
  9. Type in your NetID password and hit the Authenticate button.

If this process does not work, try using the hostname instead of


You will need to clear out the old PuTTY key in your Windows registry.

  1. Open the registry (Start/ Run/ regedit).
  2. Find the entry in the hierarchy for: HKEY_CURRENT_USER\Software\your-profile-name\PuTTY\SshHostKeys
  3. There you should see PuTTY's cache of host keys.
    1. The name column tells you which key is for which server. For example, it will have the format of [].
  4. Delete the row for the server.
  5. Using PuTTY, log back in again to You should be able to connect to the server, getting a "New Key prompt" which will say:
    The server's host key is not cached in the registry. You have no guarantee that the server is the computer you think it is... if you trust this host, hit Yes to add the key to PuTTY's cache and carry on connecting.
  6. Click Yes, and continue.

Screenshots are available in the clearing outdated RSA data tutorial from Techglimse.


macOS users who have previously logged into i4 may receive a WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! error message when trying to log in using Terminal. This occurs when server host keys change. If you receive this message, do the following:

  1. Open a new Terminal window and type: rm ~/.ssh/known_hosts
  2. Then type: ssh
    Replacing "NetID" with your actual NYU NetID
  3. You should be able to log in successfully, afterwards type exit or logout to close the Terminal window.
  4. If this doesn't work, type the following: ssh
    Replacing "NetID" with your actual NYU NetID
  5. You should be able to log in successfully, afterwards type exit or logout to close the Terminal window.


WinSCP records the host key for each server you connect to, in the configuration storage.

Verifying the Host Key

If you are using WinSCP to connect to a server for the first time, or connecting to a host whose host keys have changed, you will probably see a warning message that says something like:

Continue connecting to an unknown server and add its host key to a cache?

This warning is designed to protect you against a network attack known as spoofing: secretly redirecting your connection to a different computer, so that you send your password to the wrong machine.

Every time you connect to a server, it compares the server’s host key to the host key you received the last time you connected. If the keys differ, you will receive a warning and a chance to abandon your connection before you enter any private information such as a password.

Read more information about Verifying the Host Key »

Cleaning up your configuration file will help you remove old host keys.

Read more information about Cleaning up Application Data »