IPv6: Update

Greetings again, I am Phil King, the Product Owner of the Angry Llama Scrum team, which is actively working on IPv6.

Here is a link to a brief demo of the IPv6 features we have completed to date. Our focus thus far has been on enabling IPv6 on website content.

Our IPv6 work is currently targeted for cPanel WHM version 11.40.

Currently, we are working on tools to better handle multiple IPv6 ranges or subnets. This will enable the customers that want to break up a large allocation (e.g., a /64) into smaller ranges, and also assists the customer that gets only a handful of IPv6 addresses.
 As soon as we are finished with this feature, we will be publishing a test build to next.cpanel.net. I will provide more details on this as we get closer to that date.

With a few months of development time before our internal 11.40 deadline, now would be a great opportunity to let me know which features you would like to see next. The linked Google spreadsheet below lists upcoming features. For each feature, you can let me know how you’d feel if the feature were present, and how you’d feel if the feature were absent.


And I leave you with these questions. Take a look at your most heavily populated servers. How many users are there? How many bound IPv4 addresses do you have currently? And are your servers prepared for each of those users to have a dedicated bound IPv6 address?


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17 responses to “IPv6: Update”

  1. ali says:

    thank you . nice article 🙂
    آپلود عکس

  2. Arjen says:

    update 11.46 just killed ipv6 support in dovecot.:
    Fixed case 127357: Ensure Dovecot starts by default without ipv6 kernel module.

    ipv6 enabled dovecot config in /var/cpanel/templates/dovecot2.2/main.local is not working anymore.

    It just killed dovecot on all my cpanel servers. In my opinion cpanel is not working to a full working ipv6/ipv4 dualstack implementation.

  3. I might be wrong here, but does the number of AVAILABLE addresses really matter? Is it not the number of addresses actually used that matter for a server?

    If you have a large pool of addresses to choose from and only use one address – that should not make much of a problem? I can also see that having a lot of domains on one server with separate addresses could cause a bit more work for the server. But unused addresses?

  4. jamyn says:


  5. Joshua Whitley says:


    See page 8, second paragraph.

  6. Richard Laager says:

    I’m +1 on these features.

    Additionally, I’d like to suggest that if you’re drawing a distinction in the UI between IPv4 and IPv6, you should think really hard about whether that’s the right thing to do. It usually is not.

    For example, the “Add a New IP Address” page should not have a separate IPv6 tab, even if that means re-thinking the current design. It likely should just consist of a single textbox which takes an IP (or network or range) to add. If you enter something is a subnet of an interface already on the system, it should just add it and you’re done. If it’s not, then it should ask a follow-up question of what prefix length to use on the interface, with the default being MIN(block_is_ipv4 ? 24 : 64, mask_of_block). (And for people used to subnet masks, there’s no reason you can’t accept and convert subnet masks in the prefix length text box.) If you want to preserve the exclusions feature, that’d be part of that second step, but only for IPv4.

    Also, please use the “compressed” format when displaying IPv6 addresses. In the video, the IP shows in WHM as 2620:0000:28a0:2004:9999:0000:0000:0001 instead of 2620:0:28a0:2004:9999::1.

  7. Alex says:

    true, server cant handle that many ips.

    a /112 are 65,536 ips. so i think are enought.

  8. Anonymous Coward says:

    You are going to overload the server with such large allocations.

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  10. cpanelphil says:


    I’ll keep that request in mind: that IPv6 on SMTP should be done along with reverse DNS.

    Regarding the IPv6 and reseller tools: our first IPv6 release is a root enabled reseller tool. We will support multiple IPv6 ranges, which will enable subnets. We will likely not have a subnet delegation model for resellers in time for 11.40.

    Thank you for your input and feedback.

  11. cpanelphil says:

    Yes, the DNS files will be updated for all servers in the DNS cluster.

  12. Ryan Kearney says:

    Please specify if the following will be possible. I consider anything answered “no” to be considered a lack of IPv6 functionality.

    1. Map a /48 to a server.

    2. Assign a /58 to a reseller
    3. Allow the reseller to assign /64 to a user
    4. Allow the user to assign any address from the /64 to their domains.
    5. Ability for the end user to assign different addresses from their /64 to different addon domains.

  13. jamyn says:

    Joe, _which_ RFC states you can’t subnet anything larger than /64? There are probably over a hundred IPv6 related RFCs. How would allocating a smaller range open you up to compromise, exactly?

  14. Francisco Esteves says:

    cPanel will provide interface to configure IPv6 in cPanel DNSOnly too, right?

  15. Joe Klein says:

    Ok, so you have not read the RFC which states that the first 64 bits of an address are subnet-able (/3 – /64), and you have no ability to perform a /65 or greater unless you want to cause problems with your network and open yourself up to compromise.

  16. Mark says:

    I filled out the survey, but on some questions I had trouble providing answers, because my answer really depends on how you guys are planning to design and implement this.

    For IPv6 on smtp / exim, one of the challenges is maintaining reverse dns if each user has a unique IPv6 addr for outgoing mail.

    The “IPv6 reseller delegation” concept is confusing to me.. aren’t resellers already limited to certain IPs in the existing IPv4 setup?

    I don’t understand the part about “IPv6 subnet tool” – it seems like this question should be addressed separately on a reseller level and user level.

  17. @mariorodriguez  says:

    Thanks Phil!

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