Add a guide for configuring Cilium in direct routing mode

[joestringer]

We have getting started guides for various features and modes in Cilium, but no single clear guide on how to configure Cilium for direct routing. This is a documentation request for such a mode.

This probably involves providing different steps depending on whether nodes in the cluster are all directly connected via L2 (where --auto-direct-node-routes can help) vs. L3-connected, in which case perhaps the user needs to configure BGP or another route sharing mechanism.

[aledbf]

@joestringer is GCE using vpc-native (alias ip) in the direct routing mode scenarios?
(I am interesting in replicating the gke dataplane)

[joestringer]

@aledbf For GKE environments, yes it uses direct routing. You can see the GKE tab on the main installation guide: https://docs.cilium.io/en/stable/gettingstarted/k8s-install-helm/

[aledbf]

@joestringer yes, but I can't use GKE :( just plain GCE VMs (and using k3s)

[joestringer]

Based on this doc, I think it's possible: https://docs.cilium.io/en/stable/concepts/networking/routing/#google-cloud

It looks to me like even though the setting is marked as gke, if you use that setting in google cloud, it will still use the native google cloud networking layer. But I think that the best way to find out would be to try it. If you're running k3s, then it's also worth looking at which helm options are in the Cilium docs for installing on k3s and see which of those may be relevant to you.

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[Duanzhiwei]

I would like a guide to deploying cilium bgp mode on bare metal, but I don't know if it works and where I can get.

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[damieneichhorn]

I would like a guide to deploying cilium bgp mode on bare metal, but I don't know if it works and where I can get.

Same here, possibly including dsr

[ti-mo]

Today, this page (https://docs.cilium.io/en/stable/network/concepts/routing/#native-routing) has some pointers for running on AWS ENI and self-managed GCP, so I think the original demand of this issue is covered.

For bare metal deployments, there isn't a written guide, but our perf benchmarking suite has automation code for Cilium 1.10 (https://docs.cilium.io/en/stable/operations/performance/benchmark/#how-to-reproduce) that could be used as inspiration. It's built on Packet.net machines.

I'm afraid even accounting for L2 vs. L3-connected clusters, there are so many variables in physical deployments that any bare metal guide is bound to omit many crucial details. Also, maintaining this sort of document will be expensive because of the need for automation and hardware availability. We tend to validate all our getting started guides on every major release.