Adding IPv6 ULA to interface already configured with Prefix Delegation

[wigster]

Hello, 

My ISP delegates an IPv6 prefix but, unfortunately, it's dynamic and changes weekly. It works though and two LAN interfaces successfully have prefixes. Great!

I would now like to add a ULA to an interface but cannot see a way to add a second IPv6 address if the interface is set dynamically. For testing (please excuse the short ULA), I switched from the interface itself having a prefix delegated to having a ULA:

config ipv6
  set ip6-address fdfc:c::40/64
  set ip6-allowaccess ping https
  set ip6-send-adv enable
  set ip6-other-flag enable
  config ip6-prefix-list
    edit fdfc:c::/64
    next
  end
  config ip6-delegated-prefix-list
    edit 1
    set upstream-interface "wan1"
    set delegated-prefix-iaid 1
    set subnet 0:0:0:1::/64
   set rdnss-service default
  next
  end
end

I have (accidentally) stumbled upon a solution. It seems to work but is this actually valid configuration?

Many thanks for reading

[Anthony_E]

Hello,

Thank you for using the Community Forum. I will seek to get you an answer or help. We will reply to this thread with an update as soon as possible.

Thanks,

[Anthony_E]

Hello,

We are still looking for someone to help you.

We will come back to you ASAP.

Thanks,

[Anthony_E]

To add an IPv6 Unique Local Address (ULA) to an interface already configured with prefix delegation on a FortiGate:

1. Access the CLI: Log in to your FortiGate device using the CLI.
2. Edit the Interface: Enter the configuration mode for the specific interface where you want to add the ULA.

shell
config system interface
edit "port5" <----- Replace "port5" with your actual interface name.

3. Configure IPv6 ULA: Add the ULA to the interface configuration:

shell
config ipv6
set ip6-address fdxx:xxxx:xxxx::1/64 <----- Replace with your ULA.
end

4. Retain Existing Configuration: Ensure that the existing prefix delegation settings remain unchanged.
5. Save and Exit: Save the configuration and exit.

shell
end

[wigster]

Hi Anthony, 

Thanks for getting back to me, it's appreciated. 

If an interface is configured to use a delegated prefix, trying to set ip6-address returns an error:

(ipv6) # set ip6-address fdfc:c::40/64
Can't change dynamic IPv6.
Command fail. Return code -651

Is it actually possible to add a ULA to an interface with prefix delegation?

Thanks again

[Anthony_E]

Hello,

I really hope we will find an answer and fix your issue :)!

I will try to find an expert for your question, and will come back to you ASAP.

Regards,