- Add possibility to configure controller manager to use IPv6 dual stack:
  use `--cluster-cidr="<cidr1>,<cidr2>"`.
  Notes:
  1. Only the first two CIDRs are used (soft limits for Alpha, might be lifted later on).
  2. Only the "RangeAllocator" (default) is allowed as a value for `--cidr-allocator-type`. Cloud allocators are not compatible with IPv6 dual stack

- `-- kube-controller-manager`
  `--node-cidr-mask-size-ipv4 int32`     Default: 24. Mask size for IPv4 node-cidr in dual-stack cluster.
`--node-cidr-mask-size-ipv6 int32`     Default: 64. Mask size for IPv6 node-cidr in dual-stack cluster.

    These 2 flags can be used only for dual-stack clusters. For non dual-stack clusters, continue to use  `--node-cidr-mask-size` flag to configure the mask size.

**Action required** for Kubernetes cluster administrators and for distributions that manage the cluster Service CIDR.
Kubernetes now allows users to define the cluster Service CIDR via an API object: ServiceCIDR.

  1. When configuring a dual-stack cluster, the user must specify both `--node-cidr-mask-size-ipv4` and `--node-cidr-mask-size-ipv6` to set the per-node IP mask sizes, instead of the previous `--node-cidr-mask-size` flag.
  2. The `--node-cidr-mask-size` flag is mutually exclusive with `--node-cidr-mask-size-ipv4` and `--node-cidr-mask-size-ipv6`.

- Use NLB Subnet CIDRs instead of VPC CIDRs in Health Check SG Rules ([#93515](https://github.com/kubernetes/kubernetes/pull/93515), [@t0rr3sp3dr0](https://github.com/t0rr3sp3dr0)) [SIG Cloud Provider]

### Other (Cleanup or Flake)

* AWS kube-up: Allow VPC CIDR to be specified (experimental) ([#23362](https://github.com/kubernetes/kubernetes/pull/23362), [@miguelfrde](https://github.com/miguelfrde))
* Return "410 Gone" errors via watch stream when using watch cache ([#25369](https://github.com/kubernetes/kubernetes/pull/25369), [@liggitt](https://github.com/liggitt))

### Documentation

- Kubeadm: skip validating pod subnet against node-cidr-mask when allocate-node-cidrs is set to be false ([#98984](https://github.com/kubernetes/kubernetes/pull/98984), [@SataQiu](https://github.com/SataQiu)) [SIG Cluster Lifecycle]

- Kube-controller-manager: volume plugins can be restricted from contacting local and loopback addresses by setting `--volume-host-allow-local-loopback=false`, or from contacting specific CIDR ranges by setting `--volume-host-cidr-denylist` (for example, `--volume-host-cidr-denylist=127.0.0.1/28,feed::/16`) ([#91785](https://github.com/kubernetes/kubernetes/pull/91785), [@mattcary](https://github.com/mattcary)) [SIG API Machinery, Apps, Auth, CLI, Network, Node, Storage and Testing]...

* Avoid unnecessary spam in kube-controller-manager log if --cluster-cidr is not specified and --allocate-node-cidrs is false. ([#54934](https://github.com/kubernetes/kubernetes/pull/54934), [@akosiaris](https://github.com/akosiaris))