How to configure network load balancers

Note

Network load balancers are currently available for the OVN network.

Network load balancers are similar to forwards in that they allow specific ports on an external IP address to be forwarded to specific ports on internal IP addresses in the network that the load balancer belongs to. The difference between load balancers and forwards is that load balancers can be used to share ingress traffic between multiple internal backend addresses.

This feature can be useful if you have limited external IP addresses or want to share a single external address and ports over multiple instances.

A load balancer is made up of:

• A single external listen IP address.

• One or more named backends consisting of an internal IP and optional port ranges.

• One or more listen port ranges that are configured to forward to one or more named backends.

Create a network load balancer

Use the following command to create a network load balancer:

lxc network load-balancer create <network_name> [<listen_address>] [--allocate=ipv{4,6}] [configuration_options...]

Each load balancer is assigned to a network. Listen addresses are subject to restrictions (see Requirements for listen addresses for more information about which addresses can be load-balanced). If a listen address is not given, the --allocate flag must be provided.

Load balancer properties

Network load balancers have the following properties:

backends

List of backend specifications

Key:	backends
Type:	backend list
Required:	no

See Configure backends.

config

User-provided free-form key/value pairs

Key:	config
Type:	string set
Required:	no

The only supported keys are user.* custom keys.

description

Description of the network load balancer

Key:	description
Type:	string
Required:	no

listen_address

IP address to listen on

Key:	listen_address
Type:	string
Required:	no

ports

List of port specifications

Key:	ports
Type:	port list
Required:	no

See Configure ports.

Requirements for listen addresses

The following requirements must be met for valid listen addresses:

• Allowed listen addresses must be defined in the uplink network’s ipv{n}.routes settings or the project’s restricted.networks.subnets setting (if set).

• The listen address must not overlap with a subnet that is in use with another network or entity in that network.

• If the --allocate flag is provided, an IP address will be allocated from the uplink network’s ipv{n}.routes or the project’s restricted.networks.subnets setting (if set).

Configure backends

You can add backend specifications to the network load balancer to define target addresses (and optionally ports). The backend target address must be within the same subnet as the network that the load balancer is associated to.

Use the following command to add a backend specification:

lxc network load-balancer backend add <network_name> <listen_address> <backend_name> <listen_ports> <target_address> [<target_ports>]

The target ports are optional. If not specified, the load balancer will use the listen ports for the backend for the backend target ports.

If you want to forward the traffic to different ports, you have two options:

• Specify a single target port to forward traffic from all listen ports to this target port.

• Specify a set of target ports with the same number of ports as the listen ports to forward traffic from the first listen port to the first target port, the second listen port to the second target port, and so on.

Backend properties

Network load balancer backends have the following properties:

description

Description of the backend

Key:	description
Type:	string
Required:	no

name

Name of the backend

Key:	name
Type:	string
Required:	yes

target_address

IP address to forward to

Key:	target_address
Type:	string
Required:	yes

target_port

Target port or ports

Key:	target_port
Type:	string
Default:	same as listen_port
Required:	no

For example: 70,80-90 or 90

Configure ports

You can add port specifications to the network load balancer to forward traffic from specific ports on the listen address to specific ports on one or more target backends.

Use the following command to add a port specification:

lxc network load-balancer port add <network_name> <listen_address> <protocol> <listen_ports> <backend_name>[,<backend_name>...]

You can specify a single listen port or a set of ports. The backend(s) specified must have target port(s) settings compatible with the port’s listen port(s) setting.

Port properties

Network load balancer ports have the following properties:

description

Description of the port or ports

Key:	description
Type:	string
Required:	no

listen_port

Listen port or ports

Key:	listen_port
Type:	string
Required:	yes

For example: 80,90-100

protocol

Protocol for the port or ports

Key:	protocol
Type:	string
Required:	yes

Possible values are tcp and udp.

target_backend

Backend name or names to forward to

Key:	target_backend
Type:	backend list
Required:	yes

Edit a network load balancer

Use the following command to edit a network load balancer:

lxc network load-balancer edit <network_name> <listen_address>

This command opens the network load balancer in YAML format for editing. You can edit both the general configuration, backend and the port specifications.

Delete a network load balancer

Use the following command to delete a network load balancer:

lxc network load-balancer delete <network_name> <listen_address>