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engine: improve ipv6 subnet allocation examples 

Co-authored-by: Brennan Kinney <5098581+polarathene@users.noreply.github.com>
Signed-off-by: David Karlsson <david.karlsson@docker.com>
This commit is contained in:
David Karlsson 2023-06-01 11:22:46 +02:00
parent 18f88f0feb
commit 6f66da293c
1 changed files with 36 additions and 16 deletions
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52
config/daemon/ipv6.md
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@ -46,22 +46,18 @@ default bridge network, and to user-defined networks configured with an IPv6 sub
## Dynamic IPv6 subnet allocation
If you want dynamic IPv6 subnet allocation, you must explicitly configure the
`default-address-pools` parameter to include:
If you don't explicitly configure subnets for user-defined networks,
using `docker network create --subnet=<your-subnet>`,
those networks use the default address pools of the daemon as a fallback.
The default address pools are all IPv4 pools.
This also applies to networks created from a Docker Compose file,
with `enable_ipv6` set to `true`.
- The default address pool values
- One or more custom IPv6 supernets
To enable dynamic subnet allocation for user-defined IPv6 networks,
you must manually configure address pools of the daemon to include:
> **Note**
>
> Be aware that the following known limitations exist:
>
> - Supernets can't have a size larger than 80. This is due to an integer
> overflow in the Docker daemon. See
> [moby/moby#42801](https://github.com/moby/moby/issues/42801)
> - The difference between the supernet length and the pool size can't be
> larger than 24. Otherwise, the daemon consumes all available memory. See
> [moby/moby#40275](https://github.com/moby/moby/issues/40275)
- The default IPv4 address pools
- One or more IPv6 pools of your own
The default address pool configuration is:
@ -80,7 +76,21 @@ The default address pool configuration is:
```
The following example shows a valid configuration with the default values and
an IPv6 supernet, with a prefix length of 64 and a size of 80.
an IPv6 pool. The IPv6 pool in the example provides up to 256 IPv6 subnets of
size `/112`, from an IPv6 pool of prefix length `/104`. Each `/112`-sized
subnet supports 65 536 IPv6 addresses.
> **Note**
>
> Be aware that the following known limitations exist for IPv6 pools:
>
> - The `base` value for IPv6 needs a minimum prefix length of `/64`.
> This is due to an integer overflow in the Docker daemon.
> See [moby/moby#42801](https://github.com/moby/moby/issues/42801).
> - The difference between the pool length and the pool size can't be larger
> than 24. Defining an excessive number of subnets causes the daemon to
> consume all available memory.
> See [moby/moby#40275](https://github.com/moby/moby/issues/40275).
```json
{
@ -92,11 +102,21 @@ an IPv6 supernet, with a prefix length of 64 and a size of 80.
{ "base": "172.24.0.0/14", "size": 16 },
{ "base": "172.28.0.0/14", "size": 16 },
{ "base": "192.168.0.0/16", "size": 20 },
{ "base": "2001:db8::/64", "size": 80 }
{ "base": "2001:db8::/104", "size": 112 }
]
}
```
> **Note**
>
> The address `2001:db8` in this example is
> [reserved for use in documentation][wikipedia-ipv6-reserved].
> Replace it with a valid IPv6 network.
> The default IPv4 pools are from the private address range,
> the IPv6 equivalent would be [ULA networks][wikipedia-ipv6-ula].
[wikipedia-ipv6-reserved]: https://en.wikipedia.org/wiki/Reserved_IP_addresses#IPv6
[wikipedia-ipv6-ula]: https://en.wikipedia.org/wiki/Unique_local_address
## Next steps