Testing on network interface - promisc mode.


Hi,



I was using following steps to test the promisc mode on the network
interface on my system on FreeBSD 6.1.



- On machine A, I updated the arp table with the a dummy MAC
address (aa:bb:cc:dd:ee:ff) for the remote interface on Machine B.

#arp -s 17.1.1.110 aa:bb:cc:dd:ee:f



- On Machine B, I enabled promisc mode for the test N/W
interface.

#ifconfig <Interface> promisc



- Started tcpdump on Machine A, for capturing the packets.



- On Machine A, I ping to the remote Interface of the Machine B

#ping -c2 17.1.1.110

- Ping went through fine and Tcpdump is displaying both ICMP
request and ICMP reply.



I could understand that machine B receives ICMP request as promisc mode
is enabled. But it was not suppose to send ICMP reply as the packet was
not intended for this machine (I mean the ICMP REQUEST PACKET contain
some dummy MAC address). It was supposed to be discarded.



After testing the above steps, I could see the ICMP REPLY from MACHINE B
and ICMP REPLY contain original Mac address in the Source MAC address
field in the Ethernet header.



Please let me know whether the above behavior is correct and acceptable.



Thanks,

~Siva






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