default-address-pools¶

MCR uses three separate IP ranges for the docker0, docker_gwbridge, and ucp-bridge interfaces. By default, MCR assigns the first available subnet in default-address-pools (172.17.0.0/16) to docker0, the second (172.18.0.0/16) to docker_gwbridge, and the third (172.19.0.0/16) to ucp-bridge.

Note

The ucp-bridge bridge network specifically supports MKE component containers.

You can reassign the docker0, docker_gwbridge, and ucp-bridge subnets in default-address-pools. To do so, replace the relevant values in default-address-pools in the /etc/docker/daemon.json file, making sure that the setting includes at least three IP pools. Be aware that you must restart the docker.service to activate your daemon.json file edits.

By default, default-address-pools contains the following values:

{
  "default-address-pools": [
   {"base":"172.17.0.0/16","size":16}, <-- docker0
   {"base":"172.18.0.0/16","size":16}, <-- docker_gwbridge
   {"base":"172.19.0.0/16","size":16}, <-- ucp-bridge
   {"base":"172.20.0.0/16","size":16},
   {"base":"172.21.0.0/16","size":16},
   {"base":"172.22.0.0/16","size":16},
   {"base":"172.23.0.0/16","size":16},
   {"base":"172.24.0.0/16","size":16},
   {"base":"172.25.0.0/16","size":16},
   {"base":"172.26.0.0/16","size":16},
   {"base":"172.27.0.0/16","size":16},
   {"base":"172.28.0.0/16","size":16},
   {"base":"172.29.0.0/16","size":16},
   {"base":"172.30.0.0/16","size":16},
   {"base":"192.168.0.0/16","size":20}
   ]
 }

The default-address-pools parameters¶
Parameter	Description
`default-address-pools`	The list of CIDR ranges used to allocate subnets for local bridge networks.
`base`	The CIDR range allocated for bridge networks in each IP address pool.
`size`	The CIDR netmask that determines the subnet size to allocate from the base pool. If the `size` matches the netmask of the `base`, then the pool contains one subnet. For example, `{"base":"172.17.0.0/16","size":16}` creates the subnet: `172.17.0.0/16` (`172.17.0.1` - `172.17.255.255`).

For example, {"base":"192.168.0.0/16","size":20} allocates /20 subnets from 192.168.0.0/16, including the following subnets for bridge networks:

192.168.0.0/20 (192.168.0.1 - 192.168.15.255)

192.168.16.0/20 (192.168.16.1 - 192.168.31.255)

192.168.32.0/20 (192.168.32.1 - 192.168.47.255)

192.168.48.0/20 (192.168.48.1 - 192.168.63.255)

192.168.64.0/20 (192.168.64.1 - 192.168.79.255)

…

192.168.240.0/20 (192.168.240.1 - 192.168.255.255)