On a default installation of 11.04 desktop (running inside a VM), I'm getting a strange phenomena in which occasionally some people can't ssh into their account in the regular way (they simply get a "connection timed out"), but can connect if they change their external IP address (e.g. use iphone tethering, or a socks proxy through some remote server.)

I suspect that it may be connected to several failed connection/authentication attempts that those people reported having a short time before this IP-blocking started for each of them.

Is there anything in 11.04 that auto-blocks IPs for whatever reason? If so, what is this and how can I release a block manually? If not I guess I'll have to investigate in the host machine and in the router...


There's nothing by default that does this.

However, you may have fail2ban or something installed that is monitoring attempt logs and banning temporarily. Other than that, or sshd having built in protection, there's no reason for this.

  • and does the sshd version coming in 11.04 have such built in protection? – GJ. May 26 '12 at 1:43
  • Not that I know of, but since i'm on 12.04, i dont know. – Thomas Ward May 26 '12 at 16:37

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