How soon after the link appears (cable connection) does the switch learn the MAC address of the connected network card?

Question

Network administration

Is there any mandatory notification from the network card side in the Ethernet specification after the appearance of a physical connection? Or will the switch only get the MAC address information after sending the first packet?

Answer 1

Is there any mandatory notification from the network card side in the Ethernet specification after the appearance of a physical connection?

To be honest, I don’t know, because I have never read the specifications for 802.1D (MAC bridges) or 802.3 in their entirety . I think no. The switch (more precisely, since we are talking about specifications, bridge ) can determine the state of the physical link using L1 signaling (FLP and others).

Or will the switch only get the MAC address information after sending the first packet?

I think yes. I guess the logic here is this. A host connected to an ethernet segment must find out the MAC address of either a normal segment neighbor or a default router (which, by the way, is also its segment neighbor), for this it sends an ARP request, while actually reporting its MAC - the address in the broadcast message. At this point, the switch ( filter bridge , sorry) adds an entry to the MAC address table.
This is all true for the case of IPv4-over-Ethernet, in the case of IPv6-over-Ethernet everything is the same, with other protocols over Ethernet (I don’t even know what to assume, IPX?) I didn’t work.

Answer 2

After turning on the network interface, it sends a broadcast arp to find out some kind of dhcp or MAC address of the router if it has static network details
, well, in general, in fact, everything is a little trickier