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So I'm Network+ certified and have a beginners understanding of how network communication works, my head starts to split a bit though when I think about how the information is actually communicated between international telecoms providers and ISPs.

For the networking methodologies to hold across giant networks the way I've learned so far, I can only really think that the ISP and telecoms have basically giant ARP tables across their network infrastructure and routers.

This would seem to me to have pretty obvious implications for anyone who thinks that any of their regular internet traffic is anonymous, as the trail would be there right for any sysadmin to see on demand.

It seems very difficult to find information about how traffic is communicated once it's left your home (probably for pretty obvious reasons), is this about right?

Could someone help me fill in the blanks and potentially point me to some sources of information if available? And also please go easy on me as this is still relatively new to me!

Thanks :)

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  • MAC addresses resolved by ARP or NDP are only required and meaningful within a MAC-based layer-2 network or structure. Between those networks IP addresses are used for routing. However, requests for resources are explicitly off topic here, see the help center.
    – Zac67
    Commented Nov 3, 2023 at 19:04
  • Ah OK I wasn't aware, thanks for the link to the help center Commented Nov 3, 2023 at 19:06
  • You could use the tags on your question to check other questions and answers - you can learn a lot here, but we're not focused on tutelage or how-tos.
    – Zac67
    Commented Nov 3, 2023 at 19:19
  • Thanks though - I think I've picked up enough to make some sense of it. Effectively your home router is just another router on your ISP's network and uses normal IP routing. Commented Nov 3, 2023 at 19:31

1 Answer 1

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ARP is used to resolve a MAC address from an IPv4 address for network that use MAC addressing, and it is local to that network. MAC addresses are only seen or relevant on the specific network they are on.

ARP tables exist for each interface on a host (routers are also hosts), not across hosts. Routers will have multiple interfaces and networks, so each will have multiple ARP tables, but those ARP tables are specific to that host per network.

MAC addressing is only for delivering frames on the same network. IP addressing is for delivering packets between networks. Routers strip off frames (losing any layer-2 addressing, including MAC addressing) from the packets in order to route the packets between networks, building new frames with new layer-2 addressing for the next network.

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