I think I found the reason. In Cisco, when ABR lost connection to BACKBONE (Area 0) it becomes a regular Area N router and takes routes from another ABR in AREA N, while Bird consider that router is ABR if it has Area 0 in bird.conf, no matter if link to BACKBONE is working or not.
Am I right? So is it possible to change Bird behavior, or I need always to connect ABR via BACKBONE?
