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Your router does not use a 44-year-old protocol to build a complete inventory of every device on your network. The protocol is Address Resolution Protocol (ARP), specified in November 1982, and its narrower job is to map an IPv4 address to the Ethernet address needed to deliver traffic on the local network. A router’s connected-device list is not necessarily a direct view of its ARP table.
What is ARP?
ARP stands for Address Resolution Protocol. David C. Plummer’s RFC 826, published in November 1982, describes a method for translating protocol addresses such as IP addresses into local network addresses for transmission over Ethernet.
In practical terms, when an IPv4 device needs to send traffic to another device on the same Ethernet network, it needs the recipient’s link-layer address. ARP helps resolve that address from the recipient’s IPv4 address. The nearly 44-year-old date refers to the specification—not proof that every modern router runs an unchanged implementation from 1982.
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“Find” can mean different things. ARP performs address resolution: it helps identify the local Ethernet destination for IPv4 traffic. That is different from maintaining a complete inventory of devices connected by wire or Wi-Fi.
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A router’s client list is a feature of that router’s interface, and the cited protocol standards do not specify how a particular manufacturer builds or labels it. Do not assume that every entry in a connected-device dashboard is simply a record copied from an ARP table.
Does ARP work with IPv6?
No. ARP is associated with IPv4 address resolution over Ethernet; IPv6 uses Neighbor Discovery (ND), specified in RFC 4861. ND resolves link-layer addresses, but also supports router discovery and neighbor reachability.
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The RFC summarizes its scope this way: “IPv6 nodes on the same link use Neighbor Discovery to discover each other’s presence, to determine each other’s link-layer addresses, to find routers, and to maintain reachability information about the paths to active neighbors.” ND is not simply IPv6 ARP: it covers a broader set of functions.
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1Repair Windows errors before they cause bigger problems2Fix the driver behind crashes, sound loss and screen glitches3Clear out junk files and repair common Windows errorsDo ARP mappings last forever?
No. ARP mappings are cached, but they can become stale—for example, if a host’s Ethernet address changes. RFC 1122, published in October 1989, requires ARP implementations to provide a way to flush out-of-date cache entries. If that mechanism uses a timeout, the timeout should be configurable.
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The standard does not set one universal cache lifetime. A specific refresh interval would depend on the operating system or router implementation, so there is no single timing value that applies to every home network.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.What the age of ARP does—and does not—tell you
RFC 826’s date is a useful reminder that an internet protocol can remain foundational long after its original specification. But the date alone does not establish how many routers use ARP, whether their implementations are unchanged, or how a router decides what to show in its device list.
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ARP’s defined role is local IPv4-to-Ethernet address resolution. For IPv6, the relevant standard is Neighbor Discovery, with additional discovery and reachability functions. Neither fact, by itself, makes a router’s dashboard a complete network inventory.
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