RouterOS v3.30 on x86.
We have some pppoe servers with radius-authentication. Sometimes, our customers tune their pppoe-clients to retry every second forever. For blocked (by billing) customers we offer so-called 'gray' pppoe-session (with ip 192.168.x.x), that have access only to a few corp sites. But some of them made errors in password, use invalid logins or do other mistakes. So our radius server takes a high load to process such useless frequent queries, while they (customers) sleeps or went away to job, and etc.
Is there any method to limit these negative pppoe-session creation requests?