Wireshark mac packets on home9/7/2023 ![]() ![]() Which is the purpose of ARP, or "address resolution protocol". This means it needs some way to find out the router's MAC address. So, what if it's been 20 minutes since the last time I connected over the network? More specifically, what if it's been 20 minutes since I connected to my router? Then the router's MAC address won't be in the "ARP cache". It will only keep its contents for 20 minutes, then it's removed. That's a small file that ties IP (Internet Protocol) addresses to MAC addresses. It keeps these addresses in a file called an "ARP cache". My computer only holds onto the MAC address of the systems on the network for about 20 minutes. This is standard Ethernet (802.3) stuff.īut here's a little known (to most non-geeks) fact. When the frame gets to the router, the router changes the source and destination MAC addresses to those of itself and the server at Comcast (my ISP) that I'm tied into. ![]() However, if I'm going to send the frame outside my network, to the big Internet, then the MAC address that's used is the MAC address of my little Linksys router. If the address is for something on my network, then the connection is direct. That frame will use an address, called a "medium access control" or "MAC" address, send that frame to the next system in the link. When I use a piece of software that wants to communicate over my network, whether its just to my networked printer sitting next to my desk or to a web server sitting half-way around the world, the software will create a frame of bits. The medium, as with most home networks, is Ethernet over 100BaseT. I also have an HP printer that is wired in. I have a couple desktops hardwired with switches, along with two laptops (an HP and a MacBook) tied in wirelessly. I'm going to use my small home network for this discussion. This post will be about a truly esoteric part of the interwebs. ![]()
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