Stateless and Stateful DHCPv6 lab 8.2.3.5 question

[Sagoito]

Hello,

I was doing https://www.configrouter.com/ccna-rse-lab-configuring-stateless-stateful-dhcpv6-11188/ this lab, after i finished it I changed prefix from 2001:db8:acad:a::/64 to 2001:db8:acad:b::/64 and after i did this I got 2 ip addresses on my PC one from SLAAC one from stateful dhcpv6. I am not sure why it happens. Can somebody explain it for me? Or how i can change it to work as i want to?

[Harold Ritter]

Pretty much all hosts do SLAAC by default. If you do not want this to happen, you need to specifically configure the router so it marks the router advertisement (RA) not to be used by the host to auto configure itself. The following configuration is required in IOS to accomplish that.

Do not advertise the prefix in the RA:

ipv6 nd prefix <prefix>::/64 no-advertise

or 

Reset the A bit, which will cause the host not to use the prefix to auto configure itself:

no ipv6 nd prefix <prefix>::/64 infinite infinite no-autoconfig

Regards,