Login server blocking connections

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Revision as of 14:16, 16 February 2018 by Danielk@nikhef.nl (Talk | contribs)

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The Symptom

You are attempting to log in to login.nikhef.nl and instead of a connection you get a "no route to host" error message. Other destinations on the nikhef network - for example this wiki - are reachable for you though.

The Cause

What you are experiencing is in all likelihood not a network connectivity issue, but the result of a security system on the login.nikhef.nl server. To prevent flooding with illegitimate login attempts, this server blocks any IP address from which too many failed login attempts have been made.

In Detail

Every time a user attempts to log in and fails, a flag is raised. If this happens several times in a row, a short-term block will be enforced. If two of those short-term bans get issued in succession, a longer ban is issued. If the same happens even more regularly, the IP address gets banned indefinitely.


In case you are experiencing the symptom described above, please contact our service desk. Explain what your issue is and also provide the IP address you are connecting from when you have this problem. You can find out what your IP address is in various ways. The simplest is to just open the address https://www.iplocation.net/find-ip-address in your browser.

The helpdesk will then notify the administrators of the login server who can "unblock" your IP address.

But I did not fail on login!

It is absolutely possible that you did not directly fail to provide a username and password correctly, but you can still generate login failures. This usually happens if you have a piece of software (like and SSH or SFTP/SCP client) that offers to log in automatically as you start it. Check the following:

  • Did you recently change your password?
  • Do you have any applications which automatically connect to login.nikhef.nl?
  • Are any programs running in the background that use automatic logins? (On Windows, check the bottom right of your taskbar for that)
  • Are the login credentials still valid (i.e. is the new password entered)?

It is generally advised not to use automatic logins, but if you insist on using them, please make sure you have all passwords updated before starting up the application.

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