FreeBSD 6.3 PPPoE server problem

[soyoloo]

I am running pppoe server on freebsd 6.3. Some time when a client disconnect (manual/link lost) a pppoe session his connection in server don't automatically clear and he cant connect again until the connection is deleted manually. Here is my /etc/ppp.conf I am using static ip address from radius server for Clients

pppoein:
 set log Chat Command Phase             
 enable pap                             
 allow mode direct                    
# enable proxy                       
 disable ipv6cp                 
 set mru 1492                          
 set mtu 1492                           
 enable lqr echo
 set lqrperiod 4
 set ifaddr 172.24.0.1              
 set timeout 0
 set radius /etc/radius.conf            
 set dns 192.168.1.1 192.168.1.2
 accept dns

and tail -f /var/log/messeges output is

Jun  8 13:20:35 PPPoE ppp[30209]: Warning: iface add: ioctl(SIOCAIFADDR, 172.24.0.1 -> 172.24.1.2): File exists