Observation¶

I have noticed strange connection issues when trying to setup a VM on osiris-1.qe.nue2.suse.org (NUE-2 machine). Although the initial setup of a fresh leap image, including network connectivity, seems to be working fine (i can successfully ping and curl download.opensuse.org from within the VM), once i try to run any zypper command the connection will get stuck, without any output indicating what happened.

I was suggested to run ping commands with a higher MTU value as @okurz assumed these issues may be related to that, which seems to be correct, as those ping commands would also get stuck.

It seems only VMs on osiris-1 are affected.

Similar network-related MTU issues have been reported in previous SD tickets:

• SD-182364
• SD-142688

Steps to reproduce¶

1. Create a fresh Leap 15.6 or Tumbleweed VM on osiris-1.

2. Confirm that basic network connectivity works (ping, curl to download.opensuse.org).

3. Run zypper ref and observe that it hangs without completing.

4. Alternatively, run:

   ping -Mdo -s1442 download.opensuse.org
   

   and observe that it also hangs.

Suggestions¶

• DONE It only this one VM affected ? Try another VM on osiris
  -> ok1 also affected
• DONE Is the host itself affected ? Try on osiris-1 directly
  -> not affected
• DONE Are only VMs on osiris-1 affected ? Try another VM on another host (e.g. ada.qe.suse.de)
  -> not affected
• Consider introducing a network diagnostic hook or health check script for VM post-boot validation.

Workaround¶

Manually set the MTU size within the affected VM to a lower value, like 1360:

ip link set dev eth0 mtu 1360

This allows zypper and other network operations to proceed without hanging.