A DSL modem attached to a port on a catalyst 2924XL has, in its MAc address table, the ethernmet address assigned to the port on that switch.
eg: the ethernet address shown by:
SWITCH1>show interface fa0/23 FastEthernet0/23 is up, line protocol is up Hardware is Fast Ethernet, address is 0004.4dfd.1a97 (bia 0004.4dfd.1a97) Description: Modem1 WAN
However, if I telnet into the switch from different hosts, each host's ARP table show an ethernet address that is 1 below the first port's ethernet address. (eg: a central port-neutral MAC address).
So, under what circumstances will the switch emit packets to connected devices with those packets signed by the ethernert address associated to that port ?
Is this part of the spanning tree protocol where each port sends some broadcast signed by the port's address to see if the packet is returned to another port on the same switch ?
Are there more cases where a port will emit packets by itself ? Are there other uses for the ethernet address that is attached to each port ?