Comment 1 for bug 1926366

Triage:

This issue is ultimately caused by the apply-network-config step of the controller/worker manifest. This step launches a script that detects differences between the puppet view of what the /etc/sysconfig/network-scripts should be and what the value of the ifcfg files actually is on the system. If there are differences, the puppet view of the interface configuration is copied to the system network-scripts directory and the interface is brought down and up to apply the config. If there are no changes between the puppet view and the system view, the interface is left alone.

What happens when the underlying physical interface is configured for SR-IOV is that commands to set the number of virtual functions is added to the pre-up option in the corresponding network-script. Puppet detects this change, copies the config, and brings the interface down/up. This causes the upper vlan interfaces to lose IPv6 addresses + default route. In the case of an IPv4 system, the default route would be lost, which could be an issue in a distributed cloud environment.