Is ARP considered to be a layer 2 or layer 3 protocol ?
ARP deals with MAC addresses - it's at the MAC sublayer of the Data Link Layer.
I guess I did not google long enough before posting this question :-)
Well according to this author, (I have a hard copy of this excellent book, BTW),
<snip> describes ARP and RARP, the "oddballs" of the TCP/IP suite. In some ways they belong in both layer two and layer three, and in other ways neither. They really serve to link together the network interface layer and the internet layer. For this reason, I really believe they belong between these two and call them "layer connection" protocols </snip>
http://www.tcpipguide.com/free/t_DataLinkNetworkLayerConnectionProtocols.htm
However, for Cisco certification purposes, I believe its considered a L3 protocol.
Thanks Shahed