Adds guide for adding a hint file to the node ip configuration

[stevsmit]

Adds guide for adding a hint file to the node ip configuration

4.12

Issue:
https://issues.redhat.com/browse/OPNET-150 / https://issues.redhat.com/browse/OSDOCS-4376

Link to docs preview:

Release note: https://52200--docspreview.netlify.app/openshift-enterprise/latest/release_notes/ocp-4-12-release-notes.html#ocp-4-12-networking

Troubleshooting: https://52200--docspreview.netlify.app/openshift-enterprise/latest/support/troubleshooting/troubleshooting-network-issues.html#nw-how-nw-iface-selected_troubleshooting-network-issues

QE review:
Pending QE/SME

Original PR at #51816. Has received SME ack.

[ocpdocs-previewbot]

🤖 Updated build preview is available at:
https://52200--docspreview.netlify.app

Build log: https://circleci.com/gh/ocpdocs-previewbot/openshift-docs/5597

[rbbratta]

Linking back to old nodeip doc BZ https://bugzilla.redhat.com/show_bug.cgi?id=2105010 This should eventually resolve it.

[cybertron]

Linking back to old nodeip doc BZ https://bugzilla.redhat.com/show_bug.cgi?id=2105010 This should eventually resolve it.

Oh wow, I completely forgot I opened that. Maybe we should just remove the old method then and rely on the new override mechanism. We can always revisit this if it turns out that the new method is insufficient for someone.

[stevsmit]

@cybertron @rbbratta

To be sure, we're talking about removing the entirety of "How the network interface is selected", correct?

[cybertron]

No, we still need this section to discuss the new method. However, I think we should remove everything from "In some situations, creating a hint file might be insufficient..." on.

Also, looking at this in context a bit more I'm realizing that some of the other parts should be changed. For example, "The service iterates through the network interfaces on the node and the first network interface that is configured with a subnet than can host the IP address for the API server is selected for {product-title} communication." is describing the IPI behavior, which we do not support overriding because it breaks connectivity to the VIPs. It should say that nodeip-configuration selects the IP from the interface associated with the default route.

This is also not only relevant in case of hardware or networking changes. This is needed any time there is a networking layout where the node ip should not come from the default route interface, which is more commonly going to happen on day 1. It appears I did not review this documentation carefully enough when it was first added. :-/

[cybertron]

Okay, we still have some issues here. I left some comments inline, but overall they boil down to this should be included in the UPI docs but not the IPI docs, and it shouldn't be necessary to write a procedure to determine the available address ranges because those have to be provided as part of the installation regardless of whether you do this or not. If we just remove that section entirely a lot of the problems I noted go away.

[stevsmit]

@rbbratta @cybertron please take a look. I have made all request changes, including to the procedure and location of the docs. Thanks.

[cybertron]

/lgtm

[rbbratta]

/lgtm

[rbbratta]

/lgtm

[openshift-ci]

New changes are detected. LGTM label has been removed.