network packet's MAC address

[user0182]

this is just a quick question, that i have been unable to find a conclusive answer to on the web.

i know that when one's computer receives a network packet, that packet has many layers of information. such as the IP address of the machine from which the packet originated, in the Network Layer. my question is about the Data Link Layer of a packet, which i know includes a MAC address.

my question is; is the MAC address, stored in a network packet's Data Link Layer, the MAC address of the machine from which the packet originated, or is it the MAC address of the last machine (e.g. router) through which this packet passed?

thanks in advance for your help.


regards,

- user0182

[SirDice]

Last machine..

[Negative]

To elaborate a bit: the target IP address in the packet (Network Layer) never changes. The MAC address (Data Link Layer), on the other hand, changes at every hop - both the source and destination MAC address change every time the packet comes across a router (the source MAC address is set to that of the router's, the destination MAC address is set to that of the next hop).

[user0182]

thanks Nagative, that really helped. there is just one last thing that i was wondering about; i would guess that only hosts and routers have MAC addresses and that other devices (e.g. basic network switches) do not. is this assumption correct?


regards,

- user0182

[SirDice]

Switches (even basic ones) keep track of MAC addresses to know on which port a device is connected but you're correct about the switchport itself not having an MAC address.