ARP vs. RARP: Key Differences Explained
ARP (Address Resolution Protocol) maps an IP address to a physical MAC address on the same local network. RARP (Reverse Address Resolution Protocol) flips the process, letting a diskless machine discover its IP address when it only knows its MAC address.
Techs usually meet ARP daily when troubleshooting “Why can’t my laptop see the printer?” RARP feels like a ghost from the past—most admins have never typed it, yet it lingers in certification flashcards, causing mix-ups.
Key Differences
ARP: Client knows IP, asks “Who has this MAC?” Broadcast sent, reply unicast. Works in every IPv4 LAN today. RARP: Client knows MAC, asks “What’s my IP?” Requires a dedicated RARP server, now replaced by DHCP. ARP frames use EtherType 0x0806; RARP uses 0x8035 and is largely obsolete.
Which One Should You Choose?
Choose ARP—it’s active, automatic, and built into your OS kernel. RARP belongs in retro labs or legacy boot rooms. If you’re PXE-booting modern machines, rely on DHCP or BOOTP; forget RARP.
Is ARP still needed in IPv6?
No. IPv6 replaces ARP with Neighbor Discovery Protocol (NDP).
Can I disable ARP on a switch?
You can limit ARP via dynamic ARP inspection, but total disabling breaks local IP-to-MAC communication.
Why did RARP fade away?
RARP couldn’t supply subnet masks or gateways; DHCP offered richer configuration and took over.