ifconfig shows that a new network interface called p2p[1-N] is created when AirDrop is opened. For instance:

p2p1: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500 ether 12:9a:dd:a9:9f:1e inet6 fe80::109a:ddff:fea9:9f1e%p2p1 prefixlen 64 scopeid 0x8 media: autoselect status: active

Sniffing traffic on this interface shows mDNSv6 packets being sent to ff02::fd port 5353. Containing the strings "_airdrop", your machine name and so on.

sudo tcpdump -ni p2p1 Password: tcpdump: WARNING: p2p1: no IPv4 address assigned tcpdump: verbose output suppressed, use -v or -vv for full protocol decode listening on p2p1, link-type EN10MB (Ethernet), capture size 65535 bytes 01:56:41.647582 IP6 fe80::109a:ddff:fea9:9f1e.5353 > ff02::fb.5353: 0- [0q] 6/0/3 (Cache flush) SRV MacBook-Air.local.:57829 0 0, (Cache flush) TXT "cname=MacBook Air" "phash=MvwrscY0f8Bc5+f5vR+ncIthkl8=", PTR _airdrop._tcp.local., PTR ea4be4d626af._airdrop._tcp.local., (Cache flush) PTR MacBook-Air.local., (Cache flush) AAAA fe80::109a:ddff:fea9:9f1e (365) 01:56:41.647657 IP6 fe80::109a:ddff:fea9:9f1e > ff02::fb: frag (0|1232) 5353 > 5353: 0- [0q] 1/0/0 (Cache flush) NULL[|domain] 01:56:41.647675 IP6 fe80::109a:ddff:fea9:9f1e > ff02::fb: frag (1232|1232) 01:56:41.647686 IP6 fe80::109a:ddff:fea9:9f1e > ff02::fb: frag (2464|1232) 01:56:41.647698 IP6 fe80::109a:ddff:fea9:9f1e > ff02::fb: frag (3696|1232) 01:56:41.647704 IP6 fe80::109a:ddff:fea9:9f1e > ff02::fb: frag (4928|1232) 01:56:41.647710 IP6 fe80::109a:ddff:fea9:9f1e > ff02::fb: frag (6160|1050)

The MAC address of my Airport card in this machine is: 10:9a:dd:a9:9f:1e

Wikipedia says this about fe80::/10

fe80::/10 — Addresses in the link-local prefix are only valid and unique on a single link. Within this prefix only one subnet is allocated (54 zero bits), yielding an effective format of fe80::/64. The least significant 64 bits are usually chosen as the interface hardware address constructed in modified EUI-64 format. A link-local address is required on every IPv6-enabled interface—in other words, applications may rely on the existence of a link-local address even when there is no IPv6 routing. These addresses are comparable to the auto-configuration addresses 169.254.0.0/16 of IPv4.

[edit] and for all of those who claim that AirDrop uses some proprietary mode on the Airport card, read this:

http://hints.macworld.com/article.php?story=2011091321364956...

And ask yourself how that supposition could possibly be true when AirDrop can be made to work on Ethernet cards.