Correct. You can't use these protocols outside of the same broadcast segment[0]. That segment can be stretched though with some frame encapsulation protocol lik

Correct. You can't use these protocols outside of the same broadcast segment[0]. That segment can be stretched though with some frame encapsulation protocol like VXLAN or VPNs with bridged TAP devices. [0] Broadcast segment would be the more accurate term here, given that subnet generally refers to layer 3 addressing mechanics. Technically a broadcast segment can contain more than one operational IP subnet, but this is uncommon on most user networks.