On Wed, 31 Aug 2005, Jeff Haran wrote:
I assume you are referring to unicast packets here. I would think that
packets like this should be expected if one were to ping an attached
subnet's broadcast address.
Not even broadcasts are looped back to you over an correctly functioning
Ethernet (in CSMA/CD you don't receive while transmitting, and in full
duplex networks the switch never transmits packets out on the same port
from where it was received). Packets are only looped back if there is
loops in the Ethernet, such as is the case when bonding without support
from the switch.
Broadcasts and unicasts only differs in two aspects
- broadcasts are automatically broadcasted on all ports by switches,
while unicast packets are only broadcasted if the location of the
destination MAC is not known to the switch.
- all received broadcasts are delivered to the local IP stack, while
only unicast packets with a correct destination MAC matching the receiving
interface is delivered to the local IP stack. Unicast packets with other
destination MAC addresses are silently discarded. immediately by the NIC
if not in promiscious mode, or by the IP stack in promiscious mode as the
NIC then marks these packets differently than the packets with a correct
destination MAC for the host.
Regards
Henrik
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