This evening I setup BGP blackholing on a network of primarily Cisco. I have a few RB1100s running 4.17 that were getting BGP a few hundred bgp routes. These RB1100s were not getting any configuration related to blackholing but will see the blackholed route. The route that it sees is a /32 and its next-hop simply changes and it has a specific community and BGP localpref of 200.

When I perform this action for an IP address that's local to a Vlan interface on the Mikrotik, its routing table updates properly when it received the route. When the announcement is stopped, things go haywire. The route was no longer in the routing table but it still insists on sending traffic to the destination that was being advertised. Even pinging the IP, which is on a connected subnet, does not work. I tried to clear this up by:

* Disabling the IP on the connected subnet
* Disabling the VLAN interface on this subnet
* Hard reset of BGP sessions

Nothing cleared this issue up. The only thing I could find was to reboot the Mikrotik. I decided to upgrade to 5.11 and came across the same issue. After this I decided to setup a simple route filter and static route to blackhole this IP like it would on the other routers. Even with this in place, I ran in to the same situation.

Has anyone run in to this before? It definitely seems like a bug.