CloudFlare does not allow port 22 (usual SSH port) on domain 3

 in Applications  tagged cloudflare / DNS / port / server / ssh / ubuntu by

When you try to connect via ssh on a domain for which you are using CloudFlare as a HTTP proxy, you will get the following error:

$ ssh [email protected]
 ssh_exchange_identification: Connection closed by remote host

You have a few options to resolve for this issue:

  1. Either connect directly to the IP of the machine.
  2. Or, setup a CNAME record with no HTTP proxy for the SSH (so that you do not need to remember the IP).
    This solution does not offer any additional benefits than connecting directly to the IP of the server.
    To do that, you need to visit the configure DNS page for your site: e.g. https://www.cloudflare.com/a/dns/example.com,
    then create the CNAME named ssh, use as target your domain (e.g. example.com) and disable HTTP proxy by clicking on the orange cloud and making it gray before pressing the Add Record button.

    Then, you will be able to connect via ssh [email protected].
  3. Last solution but not least is configuring your server to listen for SSH on one of the ports of CloudFlare that are open.
    When this post was written, the following ports were available/open for any site in CloudFlare:
    For requests made via HTTP:

    80
8080
8880
2052
2082
2086
2095

    For requests made via HTTPS:

    443
2053
2083
2087
2096
8443

    At the time, we were using an Ubuntu GNU/Linux server, to instruct Ubuntu SSHD to listen to multiple ports we edited the file /etc/ssh/sshd_config and right after the lines:

    # What ports, IPs and protocols we listen for
Port 22

    we added another line with the new port we wanted to use:

    # What ports, IPs and protocols we listen for
Port 22
Port 2053

    After restarting the service
    service ssh restart;
    we were able to connect to our page as follows:
    ssh -p 2053 [email protected];

 

This post is also available in: Greek

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