Upgrades to from OpenShift 4.12 to 4.13 will also upgrade the underlying RHCOS from 8.6 to 9.2. As part of that the names of the network interfaces may change. For example `eno1` may be renamed to `eno1np0`. If a host is using NetworkManager configuration files that rely on those names then the host will fail to connect to the network when it boots after the upgrade. For example, if the host had static IP addresses assigned it will instead boot using IP addresses assigned via DHCP.

4.13

Always.

1. Select hardware (or VMs) that will have different network interface names in RHCOS 8 and RHCOS 9, for example `eno1` in RHCOS 8 and `eno1np0` in RHCOS 9.

1. Install a 4.12 cluster with static network configuration using the `interface-name` field of NetworkManager interface configuration files to match the configuration to the network interface.

2. Upgrade the cluster to 4.13.

The NetworkManager configuration files are ignored because they don't longer match the NIC names. Instead the NICs get new IP addresses from DHCP.

The NetworkManager configuration files are updated as part of the upgrade to use the new NIC names.

Note this a hypothetical scenario. We have detected this potential problem in a slightly different scenario where we install a 4.13 cluster with the assisted installer. During the discovery phase we use RHCOS 8 and we generate the NetworkManager configuration files. Then we reboot into RHCOS 9, and the configuration files are ignored due to the change in the NICs. See MGMT-13970 for more details.