dhcp for ltwp client with the same user name\password?

Hello ,
I have lt2p server with a uniqe user\pass that give IP .

now I want to add to it a a dhcp pool - so with the same user\pass it will give him a IP
for example
user test
password test
It will give it 192.168.25.0/24

how do I do it ?
so it wont affect the normal users?


I did this:

/ppp profile
add local-address=172.16.100.254 name=test-only remote-address=testing
/ip pool
add name=testing ranges=172.16.253.1-172.16.253.253

/ppp secret
add name=testing password=testing profile=test-only service=lt2p

I can see the users connecting but after 1-2 seconds they get disconnected , why?

Thanks ,