how do I configure ctr to use nexus pull through docker proxy

Question

I am in an air-gapped network, but have access to docker.io via a nexus docker pull through proxy.

I need to use ctr to pull docker.io/plndr/kube-vip.

How do I tell ctr to use nexus as a proxy?

I have added the following config to /etc/containerd/config.toml and restarted containerd

[plugin."io.containerd.grpc.v1.cri".registry.mirrors]
  [plugin."io.containerd.grpc.v1.cri".registry.mirrors."docker.io"]
    endpoint = ["http://10.13.75.3:8181"]

But I get the error

 error="failed to do request: Head \"https://registry-1.docker.io/v2/blndr/kube-vip/manifests/latest\": dial tcp: lookup registry-1.docker.io on 10.13.75.2:53: read udp 10.13.75.10:47518->10.13.75.2:53: i/o timeout" host=registry-1.docker.io

The above error shows that ctr is still trying to query DNS for an IP Address for docker.io