Today in our newest take on "older technology is better": why NAT rules!
this post was submitted on 19 Jun 2024
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Yeah, I wonder if there's any proposals to allow for multiple IPV6 addresses in Kubernetes, it would be a much better solution than NAT.
As far as I know, it's currently not possible. Every container/Pod receives a single IPv4 and/or IPv6 address on creation from the networking driver.
Even if you give it multiple ip6 cidrs to allocate?
I haven't really looked into it, but it doesn't seem like it.
Heres the documentation about having multiple cidr pools in one cluster with the Cilium network driver, and it seems to imply that each Pod only gets one IP.
https://docs.cilium.io/en/stable/network/concepts/ipam/multi-pool/
There's something called Multus that I haven't looked into, but even then it looks like that is for multiple interfaces per Pod, not multiple IPS per interface.
https://github.com/k8snetworkplumbingwg/multus-cni
Containers are just network namespaces on Linux, and all the routing is done in iptables or ebpf, so it's theoretically possible to have multiple IP addresses, but doesn't look like anybody has started implementing it. There's actually a lot of Kubernetes clusters that just use stateful IPv6 NAT for the internal Pod network, unfortunately.
Weird! Though I guess a lot of these would be sitting behind load balancers / reverse proxies anyway (so ipv4 is fine) and unlikely to up and change isps very often? Lol
If I had to, I'd be trying to add an extra cidr to one of the options listed at https://kubernetes.io/docs/concepts/services-networking/dual-stack/#configure-ipv4-ipv6-dual-stack But as you say, probably doesn't work!