Advertising an IP address pool using the community alias - Load balancing with MetalLB | Networking

About the community custom resource
Configuring MetalLB with a BGP advertisement and community alias

As a cluster administrator, you can configure a community alias and use it across different advertisements.

About the community custom resource

The community custom resource is a collection of aliases for communities. Users can define named aliases to be used when advertising ipAddressPools using the BGPAdvertisement. The fields for the community custom resource are described in the following table.

The community CRD applies only to BGPAdvertisement.

Table 1. MetalLB community custom resource
Field	Type	Description
`metadata.name`	`string`	Specifies the name for the `community`.
`metadata.namespace`	`string`	Specifies the namespace for the `community`. Specify the same namespace that the MetalLB Operator uses.
`spec.communities`	`string`	Specifies a list of BGP community aliases that can be used in BGPAdvertisements. A community alias consists of a pair of name (alias) and value (number:number). Link the BGPAdvertisement to a community alias by referring to the alias name in its `spec.communities` field.

Table 2. CommunityAlias
Field	Type	Description
`name`	`string`	The name of the alias for the `community`.
`value`	`string`	The BGP `community` value corresponding to the given name.

Configuring MetalLB with a BGP advertisement and community alias

Configure MetalLB as follows so that the IPAddressPool is advertised with the BGP protocol and the community alias set to the numeric value of the NO_ADVERTISE community.

In the following example, the peer BGP router doc-example-peer-community receives one 203.0.113.200/32 route and one fc00:f853:ccd:e799::1/128 route for each load-balancer IP address that MetalLB assigns to a service. A community alias is configured with the NO_ADVERTISE community.

Prerequisites

Install the OpenShift CLI (oc).
Log in as a user with cluster-admin privileges.

Procedure

Create an IP address pool.

Create a file, such as ipaddresspool.yaml, with content like the following example:

apiVersion: metallb.io/v1beta1
kind: IPAddressPool
metadata:
  namespace: metallb-system
  name: doc-example-bgp-community
spec:
  addresses:
    - 203.0.113.200/30
    - fc00:f853:ccd:e799::/124

Apply the configuration for the IP address pool:
```
$ oc apply -f ipaddresspool.yaml
```

Create a community alias named community1.

apiVersion: metallb.io/v1beta1
kind: Community
metadata:
  name: community1
  namespace: metallb-system
spec:
  communities:
    - name: NO_ADVERTISE
      value: '65535:65282'

Create a BGP peer named doc-example-bgp-peer.

Create a file, such as bgppeer.yaml, with content like the following example:

apiVersion: metallb.io/v1beta2
kind: BGPPeer
metadata:
  namespace: metallb-system
  name: doc-example-bgp-peer
spec:
  peerAddress: 10.0.0.1
  peerASN: 64501
  myASN: 64500
  routerID: 10.10.10.10

Apply the configuration for the BGP peer:
```
$ oc apply -f bgppeer.yaml
```

Create a BGP advertisement with the community alias.

Create a file, such as bgpadvertisement.yaml, with content like the following example:

apiVersion: metallb.io/v1beta1
kind: BGPAdvertisement
metadata:
  name: bgp-community-sample
  namespace: metallb-system
spec:
  aggregationLength: 32
  aggregationLengthV6: 128
  communities:
    - NO_ADVERTISE (1)
  ipAddressPools:
    - doc-example-bgp-community
  peers:
    - doc-example-peer

1	Specify the `CommunityAlias.name` here and not the community custom resource (CR) name.

Apply the configuration:
```
$ oc apply -f bgpadvertisement.yaml
```

Configuring community alias

About the community custom resource

Configuring MetalLB with a BGP advertisement and community alias