I don't know how to describe this issue correctly

[eshield]

Hello,

Steps to reproduce (latest snapshot):
1. Create an interface (for example, opt1);
2. Assign static IPv6 address;
3. Turn on a DHCPv6 Server on opt1;
4. Delete interface opt1;
5. Create an interface (it will be opt1 again);
6. Set IPv4 address and press "Save";
7. Get "The DHCP6 Server is active on this interface and it can be used only with a static IPv6 configuration. Please disable the DHCPv6 Server service on this interface first, then change the interface configuration." error.

I thought any interface related configuration is deleted when related interface is deleted. Deleted != Disabled.

[MikeV7896]

There's a similar issue when one creates an interface with static IPv6, then later changes it to Track Interface… DHCPv6 will continue to run, even though DHCPv6 settings cannot be modified when the interface is configured as "Track Interface". RA settings are also likely affected too.

Basically, changes to one area (interface) that affect another area (DHCPv6 and RA in this case) are not actually being changed in the affected area, allowing it to continue functioning even though its settings can no longer be modified. Of course, the issue I mention could also be resolved if feature 3029 would be implemented, but that still doesn't solve the OP's issue.