A directed ARP is the same as any other ARP, structurally. There's no difference in the packet format at all. It is used when there is more than one IPv4 subnet connected to the same router interface and allows a router to send an ARP reply that allows the actual next-hop router to be reachable directly by clients even though it's on a different subnet. Full details can be found here: https://tools.ietf.org/html/rfc1433.
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Jody Lemoine, Network Architect
CCIE 41436, MTCRE, MTCINE, MTCIPv6E
tishco networks, Virtually Everywhere
(905) 378-1134, jody.lemoine@tishco.ca
