bgp not sending notification message for malformed packet

[dharmendra kariya]

I am working with BGP implementation with Ubuntu and Cisco router. I want to do some malformation in bgp packets , bgp restrict us on size between 19 to 4096 , however for testing purpose I am changing the size less than 19 and greater than 4096 by using scapy tool. After this when I send this packet from one to second(Cisco router), on established bgp session between two speakers, the second one(Cisco) should send a notification message containing error: bad message length. But I am not getting that.

i guess even packets are not received there , because it is a malformed packet.

can anyone help me here. 

[Georg Pauwen]

Hello,

bad message length should be a facilty 3 (%BGP-3-NOTIFICATION) message, do you see anything on the receiving router with 'debug ip packet detail' enabled ? Can you tell if the malformed packet even makes it to the neighboring router, using something like Wireshark ?

[dharmendra kariya]

I tried everything, means checking logs, debugging but packets are not being reached there ( at cisco router ), nothing is there as we want, maybe because packet itself is not being received there.

I tried with sending a packet having malformed marker field ( not all field 1), by changing attribute bit values like make it as optional and transit and even partial ( every possible malfunctioning to get an appropriate notification with correspond error subcode).

at least it should receive that packet and give any response.