Good Nighttime,

I'm running libvirt 6.2 (with KVM/QEMU) on my host that has no enabled IPv6 uplink, since it is not supported by my ISP. I've created a CentOS 6 VM within that host that has a NAT-Network.

In the VM I'm able to communicate with the outside world, but when I want to build a Docker Image that pulls from ppa.launchpad.net the build process fails: Could not connect to ppa.launchpad.net:80 (, connection timed out. This is quite interesting, because other sources work.

My research so far:

  • On another system the build process works
  • On my Host-System the build process works
  • I'm able to curl the repository and ping from within the VM
  • Docker is able to pull from other sources such as archive.ubuntu.com
  • The issue is not tied to the operating system of the virtual machine

Currently I've the feeling that it might be an issue with the combination NAT and Docker Networking, but I'm unable to get the right cues to resolve it. Do you have any pointers for me?

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