To configure MetalLB, write a config map to
There is an example configmap in
annotated with explanatory comments.
The specific configuration depends on the protocol(s) you want to use to announce service IPs. Jump to:
ARP mode is the simplest to configure: in many cases, you don’t need any protocol-specific configuration, only IP addresses.
For example, the following configuration gives MetalLB control over
192.168.1.240/28 IP range, and configures ARP mode:
apiVersion: v1 kind: ConfigMap metadata: namespace: metallb-system name: config data: config: | address-pools: - name: default protocol: arp cidr: - 192.168.1.240/28
ARP mode advertises IPs into an ethernet LAN. Ethernet LANs have two
“special” IPs, the network and broadcast addresses, which cannot be
used for normal network traffic. In a typical home network like
192.168.0.0/24, the network and broadcast IPs are the
MetalLB needs to know what the network and broadcast IPs are, so that it doesn’t accidentally try to use them as service IPs.
By default, MetalLB assumes the common case: that you are trying to
advertise into a
/24 network. It will look for the
contains the IP range(s) you gave in the configuration, and use that
to figure out the network and broadcast IPs.
If you are using ARP mode on a LAN that is not
/24, you must
manually specify the network prefix using the
configuration option. MetalLB will derive the network and broadcast
IPs from that, instead of trying to deduce the values from the
For example, this is a configuration for a LAN that uses
10.0.0.0/8. We’ve allocated
10.42.42.0/24 to MetalLB.
apiVersion: v1 kind: ConfigMap metadata: namespace: metallb-system name: config data: config: | address-pools: - name: default protocol: arp arp-network: 10.0.0.0/8 cidr: - 10.42.42.0/24
For a basic configuration featuring one BGP router and one IP address range, you need 4 pieces of information:
As an example, if you want to give MetalLB the range 192.168.10.0/24 and AS number 42, and connect it to a router at 10.0.0.1 with AS number 100, your configuration will look like:
apiVersion: v1 kind: ConfigMap metadata: namespace: metallb-system name: config data: config: | peers: - peer-address: 10.0.0.1 peer-asn: 100 my-asn: 42 address-pools: - name: default protocol: bgp cidr: - 192.168.10.0/24
By default, BGP mode advertises each allocated IP to the configured
peers with no additional BGP attributes. The peer router(s) will
/32 route for each service IP, with the BGP localpref
set to zero and no BGP communities.
You can configure more elaborate advertisements by adding a
bgp-advertisements section that lists one or more custom
In addition to specifying localpref and communities, you can use this
to advertise aggregate routes. The
option lets you “roll up” the /32s into a larger prefix. Combined with
multiple advertisement configurations, this lets you create elaborate
advertisements that interoperate with the rest of your BGP network.
For example, let’s say you have a leased
/24 of public IP space, and
you’ve allocated it to MetalLB. By default, MetalLB will advertise
each IP as a /32, but your transit provider rejects routes more
/24. So, you need to somehow advertise a
/24 to your
transit provider, but still have the ability to do per-IP routing
Here’s a configuration that implemnents this:
apiVersion: v1 kind: ConfigMap metadata: namespace: metallb-system name: config data: config: | peers: - peer-address: 10.0.0.1 peer-asn: 100 my-asn: 42 address-pools: - name: default protocol: bgp cidr: - 198.51.100.0/24 bgp-advertisements: - aggregation-length: 32 localpref: 100 communities: - no-avertise - aggregation-length: 24 bgp-communities: no-advertise: 65535:65282
With this configuration, if we create a service with IP 198.51.100.10, the BGP peer(s) will receive two routes:
198.51.100.10/32, with localpref=100 and the
no-advertisecommunity, which tells the peer router(s) that they can use this route, but they shouldn’t tell anyone else about it.
198.51.100.0/24, with no custom attributes.
With this configuration, the peer(s) will propagate the
198.51.100.0/24 route to your transit provider, but once traffic
shows up locally, the
198.51.100.10/32 route will be used to forward
into your cluster.
As you define more services, the router will receive one “local”
for each of them, as well as the covering
/24. Each service you
define “generates” the
/24 route, but MetalLB deduplicates them all
down to one BGP advertisement before talking to its peers.
The above configuration also showcases the
configuration section, which lets you define readable names for BGP
communities that you can reuse in your advertisement
configurations. This is completely optional, you could just specify
65535:65281 directly in the configuration of the
/24 if you
In some environments, you’ll have some large address pools of “cheap” IPs (e.g. RFC1918), and some smaller pools of “expensive” IPs (e.g. leased public IPv4 addresses).
By default, MetalLB will allocate IPs from any configured address pool with free addresses. This might end up using “expensive” addresses for services that don’t require it.
To prevent this behaviour you can disable automatic allocation for a pool
by setting the
auto-assign flag to
# Rest of config omitted for brevity address-pools: - name: cheap protocol: bgp cidr: - 192.168.144.0/20 - name: expensive protocol: bgp cidr: - 126.96.36.199/30 auto-assign: false
Addresses can still be specifically allocated from the “expensive” pool with the methods described in the usage section.
Some old consumer network equipment mistakenly blocks IP addresses
.255, because of
If you encounter this issue with your users or networks, you can set
avoid-buggy-ips: true on an address pool to mark
addresses as unusable.