are you asking me or Judah? I work with the stuff. On Tue, May 4, 2010 at 10:26 AM, G Money <gm0n3...@gmail.com> wrote: > > Man, this takes me back to my Networking elective in college....dissecting > TCP/IP and message transport. > > Did you remember all this stuff, or do you actually work with this kind of > nuts and bolts networking stuff every day? > > On Tue, May 4, 2010 at 11:21 AM, Judah McAuley <ju...@wiredotter.com> wrote: > >> >> MAC address definitely doesn't survive out on the public internet. The >> MAC address is Layer 2, the link layer, and IP Address is Layer 3, the >> application layer. The destination IP address in a request stays the >> same through out the entire request because it is at the application >> layer. The MAC address portion of the tcp/ip packet, however, changes >> at each hop. The network devices use ARP to say, "please give me the >> MAC address of the device with this IP address" where the IP address >> is the destination of the next hop. So your computer would send out a >> packet and say "what is the MAC address of my router please?", the >> router would reply, your computer would send along the packet with the >> Layer 2 address set to the MAC of your router and then your router >> would pick it up. Then your router would ask its upstream gateway what >> its MAC address is (via ARP), swap out the Layer 2 address with the >> MAC of the upstream gateway and then send it along. In each case, what >> ever device is doing the routing creates a new frame for the Layer 2 >> info, discards the old one, and keeps the Layer 3 stuff the same. >> >> As a side note, MAC addresses are supposed to be unique. And they >> generally are. However, that hasn't always been the case. I remember >> 3Com had problems with reusing MAC addresses in their NICs in the >> mid-90s when I was doing tech support, which was quite embarrassing >> for them and potentially quite annoying for customers. >> >> Judah >> >> On Mon, May 3, 2010 at 11:05 PM, Dana <dana.tier...@gmail.com> wrote: >> > >> > they are unique. But -- I know it's complicated, cause it took most of >> > the first year of the Cisco program to get it through my head -- take >> > my word for it, even a packet capture would only show the MAC address >> > if it was on the same subnet. That's not even an expert opinion, >> > that's a fact. >> >> > >
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