I am using cocoa packet analyser because I am suspecting some intrusion. I find one special packet corresponding to arp protocol with some special ether adress. How could I find the ip related to this (I am a newbie for all these stuffs, so maybe my answer will be quite evident from you)
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May be I am wrong, but try to use wireshark
Also I think that this might be useful http://compnetworking.about.com/od/networkprotocolsip/f/convertipmacadd.htm