ARP layer in OSI model and format

Answer:

Layer 2 or 2.5 and not LAYER 3 since router not forwards the arp packet

http://networkengineering.stackexchange.com/questions/5064/on-which-layer-of-the-osi-model-does-the-arp-protocol-belong



Packet format:

Check this ARP Request capture:

Ethernet II, Src: 00:30:b8:83:cb:40, Dst: ff:ff:ff:ff:ff:ff     Destination: ff:ff:ff:ff:ff:ff (Broadcast)     Source: 00:30:b8:83:cb:40  (00:30:b8:83:cb:40 )     Type: ARP (0x0806)     Trailer: FFE000200020003035800000FFE000100030              Address Resolution Protocol (request)     Hardware type: Ethernet (0x0001)     Protocol type: IP (0x0800)     Hardware size: 6     Protocol size: 4     Opcode: request (0x0001)     Sender MAC address: 00:30:b8:83:cb:40 (00:30:b8:83:cb:40)     Sender IP address: 201.6.115.1 (201.6.115.1)     Target MAC address: 00:00:00_00:00:00 (00:00:00:00:00:00)     Target IP address: 201.6.115.254 (201.6.115.254)

http://cauew.blogspot.in/2008/08/arp-rarp-proxy-arp-gratuitous-arp-and.html
http://www.tcpipguide.com/free/t_ARPMessageFormat.htm
http://wiki.wireshark.org/AddressResolutionProtocol