I'm curious about the reason behind the decision to only support IPv6. Can you elaborate?

At a high level, It was easier to implement because we can encode information into the IPv6 address such as the destination container, source container, and a few other things.

But with that said, we now have IPv4 private networking in beta:

https://railway.com/changelog/2025-09-19-railpack-default#ipv4-private-networks-to-priority-boarding-

Awesome! This was pushing back our migration from Heroku to Railway as it required us to swap for libraries that support ipv6.

Nice to see IPv4 finally coming, nice work.

Will this be available in legacy IPv4 environments? Currently, I have to create a new project and migrate all the services there, and I have a lot of them. I'd like this feature to be available in legacy projects as well. When will this feature be available in legacy environments?

When this feature is GA'd IPv4 will be available in pre-existing environments.

Is there an ETA for the GA ?

No ETA yet unfortunately.

Have just put this feature into GA

We will be enabling it on all pre-existing environments next week.

awesome! thank you

I can't wait to try this out, what do i need to do to enable in my existing (legacy) production environment so that traffic between my services is private? Please link to docs on how. Thank you!

Also, many announcements refer to "Private Boarding" but for the life of me I can't figure out what Railway is referring to by this term.

You mean priority boarding, a train term that in the context of Railway simply means the beta testers program.

https://railway.com/account/feature-flags

As phin mentioned above, the feature is already generally available for new environments, and we will be enabling it on already existing environments in the next week, nothing you need to do on your end, we will update this thread one we have enabled it on all environments.

Additionally, given the wording you used, I need to mention that we already have private networking that has been generally available for well over a year now, but that has been IPv6 only.

Thank you, now I see what you mean about Priority Boarding, I didn't know those feature flags existed.

I was aware of the IPV6 option but it is a pain to migrate our services to IPV6... some things didn't seem to work right. So looking forward to IPv4 support (as backwards as that sounds!)

Hello from the next week. Is it enabled in existing environments yet?

Also, is there any change to the DNS in tailscale ? See attached

Not yet, unfortunately, other stuff came up that needed the engineer's attention.

Rest assured, we will update here once it is enabled on existing environments.

And if your Tailscale subnet router works now, then no changes will be needed to your DNS configurations.

Any updates on when can we expect this on existing environments?

No updates, sorry. The previous message I sent would still be the status quo.

What is the status on this feature ? When is it going to be shipped?

IPv4 private networking is GA for all new environments.

Hi team, is there a timeline for extending this feature to existing environments? Understanding the ETA would help us plan accordingly, as recreating our environments from scratch would require significant effort.

We are not able to offer an ETA at this time, apologies.

Note that I would prefer not having IPv4 anywhere so have Legacy IP be optional please

ETA?