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My local IP/subnet is 10.33.19.*/24, and yet I am occasionally receiving broadcasts requesting information from and concerning IPs in the 10.17.*.* range. I was of the impression that ARP requests do not pass through subnets. Am I wrong?

Idunnoanymore
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You are confusing different network layers. An IP address exists in layer 3, the network layer. A MAC address exists in the link layer, layer 2. The purpose of ARP is to find out (by layer 2 broadcast) which layer 2 address (MAC) a particular layer 3 address (IP) is associated with.

To put it another way, it is possible for multiple L3 addresses (IP subnets) to exist on the same L2 segment (switch or VLAN), so its perfectly valid to see ARP messages for subnets that you don't necessarily use on the machine where you see such messages.

ThatGraemeGuy
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  • Can you explain how a network could be setup to have multiple subnets on the same lan? The only networks I ever really work with are as follows: A tree hierarchy of routers, with many meshes of dumb switches, each mesh connected to the router hierarchy such that one and only one of the switches in any given mesh are connected to a singular router. As it may be obvious: networking isn't really my job :P. – Idunnoanymore Aug 26 '20 at 03:45