i am getting dynamic ip's but ip is not assigned from the pool i given .Can you please give me some suggestion

i had given

ippool main_pool {

                # range-start,range-stop: The start and end ip
                # addresses for the ip pool
                range-start =10.143.71.15
                range-stop =10.143.71.25

But i got output as

Service-Type = Framed-User
Framed-Protocol = PPP

        Framed-IP-Netmask = 255.255.255.0
        Framed-Routing = Broadcast-Listen
        Framed-Filter-Id = "std.ppp"
        Framed-MTU = 1500

Framed-Compression = Van-Jacobson-TCP-IP
Framed-IP-Address = 192.168.2.40

and i found this ips will varies with nas port