- `-- 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.

- Since golang 1.17 both net.ParseIP and net.ParseCIDR rejects leading zeros in the dot-decimal notation of IPv4 addresses,
  Kubernetes will keep allowing leading zeros on IPv4 address to not break the compatibility.
  IMPORTANT: Kubernetes interprets leading zeros on IPv4 addresses as decimal, users must not rely on parser alignment to not being impacted by the associated security advisory:

- File content check for IPV4 is now enabled by default, and the check of IPV4 or IPV6 is done for `kubeadm init` or `kubeadm join` only in case the user intends to create a cluster to support that kind of IP address family ([#115420](https://github.com/kubernetes/kubernetes/pull/115420), [@chendave](...

- `kubelet` allows pods to use the `net.ipv4.tcp_fin_timeout`, “net.ipv4.tcp_keepalive_intvl”
  and “net.ipv4.tcp_keepalive_probes“ sysctl by default; Pod Security Admission
  allows this sysctl in `v1.29+` versions of the baseline and restricted policies. ([#121240](https://github.com/kubernetes/kubernetes/pull/121240), [@HirazawaUi](https://github.com/HirazawaUi))
- `kubelet` now allows pods to use the `net.ipv4.tcp_keepalive_time` sysctl by default

### (No, really, you MUST read this before you upgrade)

- [IPv4/IPv6 dual-stack](https://kubernetes.io/docs/concepts/services-networking/dual-stack) enables the allocation of both IPv4 and IPv6 addresses to Pods and Services.

- Kube-proxy: Added dual-stack IPv4/IPv6 support to the iptables proxier. ([#82462](https://github.com/kubernetes/kubernetes/pull/82462), [@vllry](https://github.com/vllry)) [SIG Network]

### IPv4/IPv6 run

- Kube-proxy doesn't set the sysctl `net.ipv4.conf.all.route_localnet=1` if no IPv4 loopback address is selected by the `nodePortAddresses` configuration parameter. ([#107684](https://github.com/kubernetes/kubernetes/pull/107684), [@aojea](https://github.com/aojea))

- IPVS proxier now set net/ipv4/vs/conn_reuse_mode to 0 by default, which will highly improve IPVS proxier performance. ([#71114](https://github.com/kubernetes/kubernetes/pull/71114), [@Lion-Wei](https://github.com/Lion-Wei))