![]() Several useful protocols operate at the Link Layer level, like ARP, OSPF, PPP, MAC (including Ethernet).īasically, at the Link-Layer level, you need no routing because packets destined to other hosts are sent on the wire for anyone to listen to all hosts on the physical connection receive the packet, those to which it is not addressed discard it, while only the true addressee keeps it to read it. Link-level addresses belong to the so called Link Layer, which is a mix of OSI Layer 1 (physical) and OSI Layer 2 (Data Link Layer) concepts. It also follows that these addresses do not need any gateway, because they are not even supposed to evade into a different network. Thus these addresses are not used to reach hosts outside your local network, or, in technical lingo, they are not routable: once packets with these addresses reach a gateway (the junction between 2 or more distinct networks), the gateway discards them. i.e, an address that operates only on the network the host is physically connected to. The expression link#x, where x is some digit, is used to indicate that the corresponding address is a link-level address.
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