In configuration of MA5200F, a command of ppp connection chasten 5 300 3000 is configured. It means that if a user dials five time within 300 seconds, it will be screened out for 3000 seconds; at the same time, partial links of switch under MA5200F are not stable, resulting in frequent dropping offline of users. The dropped users will dial many time in a short time until it they are screened out once reaching the restrictions on ppp continuous dialing.
EXecute the ppp connection chasten 10 300 3000 command to change the restriction value; at the same time, ensure the stability of links at lower layer. The problem is solved. 

1. The configuration of MA5200F is problematic;
2. Users and MA5200F fail in ppp flow;
3. Users are illegal;
The problem is caused by restriction on dial-up times for PPP users under MA5200F, and partial users cannot access network after dialing many times with a specific time