Merge pull request #75492 from slovern/TELCODOCS-1682

TELCODOCS-1682 - MetalLB - FRRK8s integration

Author: skrthomas

_topic_maps/_topic_map.yml

@@ -1619,6 +1619,8 @@ Topics:
     File: metallb-configure-services
   - Name: Managing symmetric routing with MetalLB
     File: metallb-configure-return-traffic
+  - Name: Configuring the integration of MetalLB and FRR-K8s
+    File: metallb-frr-k8s
   - Name: MetalLB logging, troubleshooting, and support
     File: metallb-troubleshoot-support
 - Name: Associating secondary interfaces metrics to network attachments

images/695_OpenShift MetalLB_FRRK8s integration_0624.png

@@ -0,0 +1,30 @@
+// Module included in the following assemblies:
+//
+// * networking/metallb/metallb-frr-k8s.adoc
+
+:_mod-docs-content-type: PROCEDURE
+[id="nw-metallb-configuring-frr-k8s_{context}"]
+= Activating the integration of MetalLB and FRR-K8s
+
+The following procedure shows you how to activate `FRR-K8s` as the backend for `MetalLB`.
+
+.Prerequisites
+
+* You have a cluster installed on bare-metal hardware.
+* You have installed the OpenShift CLI (`oc`).
+* You have logged in as a user with `cluster-admin` privileges.
+
+.Procedure
+
+* Set the `bgpBackend` field of the `MetalLB` CR to `frr-k8s` as in the following example:
++
+[source,yaml]
+----
+apiVersion: metallb.io/v1beta1
+kind: MetalLB
+metadata:
+  name: metallb
+  namespace: metallb-system
+spec:
+  bgpBackend: frr-k8s
+----

modules/nw-metallb-configuring-frr-8ks.adoc

@@ -0,0 +1,59 @@
+// Module included in the following assemblies:
+//
+// * networking/metallb/metallb-frr-k8s.adoc
+
+:_mod-docs-content-type: REFERENCE
+[id="nw-metallb-configuring-frr-k8s-configuratons_{context}"]
+= FRR configurations
+
+You can create multiple `FRRConfiguration` CRs to use `FRR` services in `MetalLB`. 
+`MetalLB` generates an `FRRConfiguration` object which `FRR-K8s` merges with all other configurations that all users have created.
+
+For example, you can configure `FRR-K8s` to receive all of the prefixes advertised by a given neighbor.
+The following example configures `FRR-K8s` to receive all of the prefixes advertised by a `BGPPeer` with host `172.18.0.5`: 
+
+.Example FRRConfiguration CR
+[source,yaml]
+----
+apiVersion: frrk8s.metallb.io/v1beta1
+kind: FRRConfiguration
+metadata:
+ name: test
+ namespace: metallb-system
+spec:
+ bgp:
+   routers:
+   - asn: 64512
+     neighbors:
+     - address: 172.18.0.5
+       asn: 64512
+       toReceive:
+        allowed:
+            mode: all
+----
+
+You can also configure FRR-K8s to always block a set of prefixes, regardless of the configuration applied. 
+This can be useful to avoid routes towards the pods or `ClusterIPs` CIDRs that might result in cluster malfunctions. 
+The following example blocks the set of prefixes `192.168.1.0/24`:
+
+.Example MetalLB CR
+[source,yaml]
+----
+apiVersion: metallb.io/v1beta1
+kind: MetalLB
+metadata:
+  name: metallb
+  namespace: metallb-system
+spec:
+  bgpBackend: frr-k8s
+  frrk8sConfig:
+    alwaysBlock:
+    - 192.168.1.0/24
+----
+You can set `FRR-K8s` to block the `Cluster Network` CIDR and `Service Network` CIDR. 
+You can view the values for these CIDR address specifications by running the following command: 
+
+[source,terminal]
+----
+$ oc describe network.config/cluster
+----