Blackhole BGP Configuration in Mikrotik

 Code:

1   chain=to_MYISP prefix=xxx.xxx.xx.0/22 prefix-length=32 action=accept bgp-communities=1111:111

2   chain=to_MYISP prefix=xxx.xxx.x.0/22 prefix-length=22-24 action=accept 

3   chain=to_MYISP action=discard

(note that rule 1 uses BGP match "bgp-communities=" and not BGP action "set-bgp-communities")

Whenever you need to blackhole something:

/ip route add dst=b.b.b.b/32 bgp-communities=1111:111 type=blackhole

Whenever you want to lift the blackhole, just disable or remove the route.

The filters won't need to get touched anymore.