PPPoE Connection problem

Hellow,I have a problem related with pppoe connection let me first explain the situation,

I have a mikrotik router os pppoe server and my clients are all UBNT devices and they are in router mode in network settings and pppoe chosen.
So the system works correctly there is no problem with working but only one problem is this that,when a customer’s internet expires mikrotik finishes the account login but the ubnt device always tries to login and that makes my server tierd and makes a lot of log file and allocates space in the disk so how can I prevent this is there any choice ?

ppp redail… heh - a pain in many cpe devices

Allow them to connect, but firewall them? Nothing you can really do to stop the cpe from attempting to re-authenticate, unless you can configure the cpe not to do so.

what should be the firewall settings ? how can you show me the configration

so ??

please just answer me