Question Weird Plesk ip6 assignment/lock behaviour

[s.kazimierczak]

Server operating system version

Debian 12.11

Plesk version and microupdate number

18.0.71

I have Plesk 18.0.71 on Debian 12.11. I noticed a weird behaviour and I don't know if it's normal or not.
When I create a subscription when I'm logged in as admin and under admin and in the hosting parameters IP6 is set to NONE (I have IP6 setup as dedicated under Tools&Settings->IP addresses) aftrer subscription is created it basically locks/removes the ability to choose IP6 for other domains on other subscriptions under different customers. The drobdown in other websites Hosting settings is just removed. When I delete this subscription it appears again. When I create a subscription under a regular customer and IP6 is selected to NONE it works normal and the dropdown for IP6 is available for all other customers and their subscriptions.

 

[LRLD]

If the IPv6 address is set to dedicated it will only be available to the site you have chosen.
You need to set it (the IPv6 address) to shared to be able to use it on all of your sites/subscriptions.
I hope that answers your question.

Regards

 

[s.kazimierczak]

If the IPv6 address is set to dedicated it will only be available to the site you have chosen.
You need to set it (the IPv6 address) to shared to be able to use it on all of your sites/subscriptions.
I hope that answers your question.

Regards

Not entirely. As stated above none of the domain bad it assigned. I added a subscription under user admin and in creation process the ip6 was set to NONE and it immediately locked it for other customers. I couldn’t fin any answer on internet so I asked ChatGPT and the answer was that this is How Plesk works when you add subscription under admin it automatically lock it even if set to NONE in creation process.

 

[Kaspar]

This does sound like odd behavior, however I am unable to replicate the issue on my test server.

Just to be sure, when you create a subscription does the IPv6 options default to NONE already or does it defaults to an IPv6 address already?

When I create a subscription under a regular customer and IP6 is selected to NONE it works normal and the dropdown for IP6 is available for all other customers and their subscriptions.

These actions are performed while logged in as an administrator, right?

 

[s.kazimierczak]

This does sound like odd behavior, however I am unable to replicate the issue on my test server.

Just to be sure, when you create a subscription does the IPv6 options default to NONE already or does it defaults to an IPv6 address already?


These actions are performed while logged in as an administrator, right?

Hi, thanks for replay. Yes it defaults to NONE. And yes, I’m logged in as administrator. I’m creating subscription directly in subscriptions when logged as admin. When I done that the Ip6 dropdown appear only for subscriptions owned by admin. When I deleted it the dropdown is again available for all. When I create the same subscription but from the Customers page under some customer it doesn’t lock the dropdown of IP6 in Hosting settings.

 

[s.kazimierczak]

This does sound like odd behavior, however I am unable to replicate the issue on my test server.

Just to be sure, when you create a subscription does the IPv6 options default to NONE already or does it defaults to an IPv6 address already?


These actions are performed while logged in as an administrator, right?

And this is the reply for the same question from ChatGPT:

✅ What’s happening (in simple terms)​

In Plesk:

• IP addresses can be “shared” or “dedicated.”
• If you assign an IP (IPv4 or IPv6) to a subscription as “dedicated,” it’s reserved exclusively for that subscription.
• If you don’t assign it, the behavior depends on how the subscription is created and under whom.

When you create a subscription as the admin, Plesk treats the IP binding globally because the admin technically owns all resources. So:

• If you set IPv6 to None while creating as admin, Plesk treats the dedicated IPv6 as “reserved but unused.”
• Since it’s dedicated, it’s locked out for other customers — but because the subscription doesn’t use it, no one else can either.
• Result: The dropdown for IPv6 is gone for other subscriptions.

However, if you create a subscription under a customer, Plesk respects the standard customer-level allocation. The unused dedicated IP is not locked at the global level — so the dropdown stays visible.

---

✅ So, is this normal?​

Yes — it’s consistent with how Plesk handles IP allocation. But it’s counterintuitive because:

• An unused IP feels like it should remain available.
• But “dedicated” means it’s reserved for that subscription exclusively, even if unused.
• When created by admin, Plesk doesn’t split “admin-owned pool” vs. “customer pool” clearly in this case.

---

How to avoid it​

1️⃣ If you want that IPv6 to stay available:

• Don’t set it as “dedicated.”
• Or, make sure you assign it properly during subscription creation, don’t leave it as None.
• Or, create subscriptions under a customer instead of directly as admin, to prevent this edge case.

2️⃣ Check your IP pool settings:

• Go to Tools & Settings → IP Addresses.
• Make sure your IPv6 is set as Shared if you want multiple subscriptions/customers to use it freely.

3️⃣ If you want to keep it Dedicated for some sites but share for others:

• You may need to split your IP blocks or add multiple IPv6 addresses to the server.
• Assign one as Shared, keep the other as Dedicated.

---

✅ Bottom line​

You didn’t do anything wrong — this is just Plesk’s design. But you can avoid it by:

• Changing the IP to Shared if you want multiple subscriptions to pick it.
• Or making sure any Dedicated IP is actually assigned when creating a subscription as admin.

---

If you’d like, I can help you write the exact steps to fix it or adjust your setup so this doesn’t block you in the future. Just say so!

 

[Kaspar]

Hi, thanks for replay. Yes it defaults to NONE. And yes, I’m logged in as administrator. I’m creating subscription directly in subscriptions when logged as admin. When I done that the Ip6 dropdown appear only for subscriptions owned by admin. When I deleted it the dropdown is again available for all. When I create the same subscription but from the Customers page under some customer it doesn’t lock the dropdown of IP6 in Hosting settings.

So, just to recapitulate the issue; you have an IPv6 address configured on the server which is set as a dedicated address. Then, when you create a new subscription for the admin account (while being logged on as the admin user) and do NOT select any IPv6 address for the subscription (leaving the drop down value to NONE) the IPv6 option becomes unavailable for all other subscriptions, expect the subscriptions owned by the admin?

That's definitely not intended behavior. However since I am unable to replicate the issue I am not sure if it's a bug or caused by some specific configuration on your server.

Could you try one more thing to see if it makes any difference. After you've created the admin subscription and the IPv6 option becomes unavailable/locked for other subscription, can you log out of Plesk and log back in to see if the IPv6 option is available again on the other subscriptions?