Is it possible to use Federation without having public DNS records

[wsdookadr]

I wish it were possible to use Federation without such high requirements.
Maybe it's possible to just use a public IP instead of having to do the entire DNS entries and so on?

I also feel like the documentation could contain a checklist of requirements for federation to actually be possible.

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Ideally it should be possible to also have a one-way federation where I can have a matrix server A in my homelab that just pulls messages from B and is also able to send messages in B but B is not allowed to have users in A. This should do away with the need for public IP for A.
Is this possible currently?