CNI is a set of network tooling that caters to container-based network requirements. CNI uses a plugin development model to accommodate different network functions and requirements. Podman can use many of these plugins directly to easily set up basic networking for individual containers, or for containers running within a pod.

You can opt to use CNI as the default network backend to maintain consistent configuration with older Podman deployments.

To use CNI, you must have the containernetworking-plugins package installed. To check whether this package is installed, use:

rpm -q containernetworking-plugins

If it's not installed, install it using:

sudo dnf install -y containernetworking-plugins

For each network you create in Podman, a new configuration file in JSON format is generated in the /etc/cni/net.d/ directory. In most instances, you don't need to edit or manage the files in this directory.

A typical network configuration file might look similar to:

{
   "cniVersion": "0.4.0",
   "name": "mynetwork",
   "plugins": [
      {
         "type": "bridge",
         "bridge": "cni-podman1",
         "isGateway": true,
         "ipMasq": true,
         "hairpinMode": true,
         "ipam": {
            "type": "host-local",
            "routes": [
               {
                  "dst": "0.0.0.0/0"
               }
            ],
            "ranges": [
               [
                  {
                     "subnet": "10.89.0.0/24",
                     "gateway": "10.89.0.1"
                  }
               ]
            ]
         },
         "capabilities": {
            "ips": true
         }
      },
      {
         "type": "portmap",
         "capabilities": {
            "portMappings": true
         }
      },
      {
         "type": "firewall",
         "backend": ""
      },
      {
         "type": "tuning"
      }
   ]
}

Netavark is a high-performance network stack that can be used to configure network bridges, firewall rules, and system settings for containers. Netavark doesn't use plugins to perform configuration setup. All network set up actions are performed directly by the tool itself, which reduces overhead, and improves network setup performance when you run a container. Netavark provides improved handling of IPv6, Network Address Translation (NAT) and port forwarding. DNS is also automatically configured across networks so that containers with several networks can connect to any other container on any other shared network by using the container name as a resolvable DNS reference.

Use the Netavark backend if all deployments are using Podman version 4.0 or later and you intend only to run containers within Podman. Netavark provides better performance and features that make containers easily integrate into existing network infrastructure and improved DNS resolution.

To use Netavark, you must have the netavark package installed. To check whether this package is installed, use:

rpm -q netavark

If it's not installed, install it using:

sudo dnf install -y netavark

For each network that you create within Podman, a new configuration file in JSON format is generated in the /etc/containers/networks/ directory. In most instances, you don't need to edit or manage the files within these directories.

A typical network configuration file might appear as follows:

{
     "name": "mynetwork",
     "id": "3977b0c90383b8460b75547576dba6ebcf67e815f0ed0c4b614af5cb329ebb83",
     "driver": "bridge",
     "network_interface": "podman1",
     "created": "2022-09-06T12:08:12.853219229Z",
     "subnets": [
          {
               "subnet": "10.89.0.0/24",
               "gateway": "10.89.0.1"
          }
     ],
     "ipv6_enabled": false,
     "internal": false,
     "dns_enabled": true,
     "ipam_options": {
          "driver": "host-local"
     }
}

You can display the contents of a network configuration file with the following command:

sudo podman network inspect network_name

1. Check whether /etc/containers/containers.conf exists. If not, copy the default configuration to this location so that you can customize it for the deployment.

   sudo cp /usr/share/containers/containers.conf /etc/containers/

2. Edit /etc/containers/containers.conf and find the network_backend entry in the [network] section of the configuration file. Remove the entry's comment character if it exists. Change the value to match the network backend that you would prefer to use. For example, to use the CNI backend, change the entry to match:

   network_backend = "cni"

3. Reinitialize the Podman configuration to its pristine state:

   sudo podman system reset

   This command displays a warning and prompts you for confirmation.

   WARNING! This will remove:
           - all containers
           - all pods
           - all images
           - all networks
           - all build cache
           - all machines
   Are you sure you want to continue? [y/N] y

   Note:

   If you have non root Podman instances, these also need to be reset individually if the network stack is changed.

4. Reboot the system to ensure that the networking is running correctly for Podman to function.