Article ID: 122073, created on Jun 18, 2014, last review on Sep 15, 2016

  • Applies to:
  • Plesk 12.5 for Linux
  • Plesk 12.0 for Linux
  • Plesk 11.0 for Linux
  • Plesk 11.5 for Linux
  • Plesk 12.5 for Windows
  • Plesk 12.0 for Windows
  • Plesk 11.5 for Windows



Running the Plesk Daily Maintenance Task or clicking the Retrieve Keys button (at Tools&Settings > License Management ) fails with the following error:

curl: (7) Failed to connect to 2001:4168:1236::80: Network is unreachable

In the user interface, the following error may appear:

cURL error description: Failed to connect to port 5224: Network unreachable(7)



  • cURL bug. Inappropriate handling of interface availability:

    cURL tries to use IPv6 even though it is not configured properly (the IPv6 network is unreachable) and does not retry with IPv4 after a failure.
  • IPv6 stack misconfiguration:

    The IPv6 stack is configured but is not working (cannot be used to transmit/receive data). As a result, cURL fails when trying to connect via IPv6.

Related bug.


  1. In any system, you can force cURL to drop its name resolution attempts by specifying the address of KA server in the appropriate hosts file (/etc/hosts for Linux and C:\Windows\System32\drivers\etc\hosts for Windows):
  2. Disable IPv6.

    Note: Use it at your own risk!

    On Linux, you can try to disable the IPv6 protocol by adding the following lines to /etc/sysctl.conf:

    net.ipv6.conf.all.disable_ipv6 = 1
    net.ipv6.conf.default.disable_ipv6 = 1
    net.ipv6.conf.lo.disable_ipv6 = 1 

    Alternatively, execute the following command:

    echo 1 > /proc/sys/net/ipv6/conf/all/disable_ipv6

    On Windows, IPv6 tunneling interfaces can be disabled with the following commands:

    netsh interface ipv6 6to4 set state disabled
    netsh interface teredo set state disabled

    IPv6 for a real interface can be disabled via the user interface:


    IPv4 only

    You can also set the curl option when using it from PHP, as follows:

    curl_setopt($ch, CURLOPT_IPRESOLVE, CURL_IPRESOLVE_V4 );

Search Words

Please activate the plesk panel key

network unreachable

code 1603

curl Network is unreachable


licence key

Network is unreachable

Error: Unable to connect to license server cURL error description: Failed to connect to port 5224: Network unreachable(7)

Failed to connect

"Unable to connect to license server cURL error description: Failed to connect to port 5224: Timed out(7) "

curl failed

Unable to connect to license server

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