yeah, i had looked into the logs but I diddn't see anything strange, here is the last part of the logs, i'm using the command "log filetolog.log all;"

Log of H3, the one that i killed with kill -9:

2018-05-17 14:03:50.710 <TRACE> h3_3_h4_4: Got KEEPALIVE
2018-05-17 14:03:50.972 <TRACE> h3_3_h2_2: Sending KEEPALIVE
2018-05-17 14:03:51.178 <TRACE> h3_3_h2_2: Got KEEPALIVE
2018-05-17 14:03:51.517 <TRACE> h3_3_h4_4: Sending KEEPALIVE
2018-05-17 14:03:51.533 <TRACE> device1: Scanning interfaces
2018-05-17 14:03:51.534 <TRACE> h3_3_h4_4: Got KEEPALIVE

-----here the log is brusquely interruptet by the kill -------

here is the log of H2 (with htop i see that the process is interruptet with the process of H3):

2018-05-17 14:03:51.290 <TRACE> h2_2_h1_1: Got KEEPALIVE
2018-05-17 14:03:51.535 <TRACE> device1: Scanning interfaces
2018-05-17 14:03:51.608 <TRACE> h2_2_h3_3: Connection closed
2018-05-17 14:03:51.608 <TRACE> h2_2_h3_3: BGP session closed
2018-05-17 14:03:51.608 <TRACE> h2_2_h3_3: State changed to stop
2018-05-17 14:03:51.608 <TRACE> h2_2_h3_3 > removed [sole] 100.1.2.0/24 unicast
2018-05-17 14:03:51.608 <TRACE> kernel1 < removed 100.1.2.0/24 unicast
2018-05-17 14:03:51.608 <TRACE> h2_2_h1_1 < removed 100.1.2.0/24 unicast

here the log of H4:

2018-05-17 14:14:53.662 <TRACE> device1: Scanning interfaces
2018-05-17 14:14:53.732 <TRACE> h4_4_h3_3: Connection closed
2018-05-17 14:14:53.732 <TRACE> h4_4_h3_3: BGP session closed
2018-05-17 14:14:53.732 <TRACE> h4_4_h3_3: State changed to stop
2018-05-17 14:14:53.733 <TRACE> h4_4_h3_3 > removed [sole] 100.1.1.0/24 unicast
2018-05-17 14:14:53.733 <TRACE> kernel1 < removed 100.1.1.0/24 unicast
2018-05-17 14:14:53.733 <TRACE> h4_4_h5_5 < removed 100.1.1.0/24 unicast

all the log is brusquely interruptet, and i don't know why.

and after this...do you know if there is in bird some check in the interface if it is already on? so if i disable the interface beetween the host could i reach the result that i want?

thanks,

Mattia