Get Router's MAC Address

>> traceroute google.com
traceroute: Warning: google.com has multiple addresses; using 173.194.72.138
traceroute to google.com (173.194.72.138), 64 hops max, 52 byte packets
1 172.18.87.254 (172.18.87.254) 2.781 ms 39.006 ms 4.022 ms
2 140.113.136.222 (140.113.136.222) 2.771 ms 34.815 ms 2.666 ms
3 140.113.0.74 (140.113.0.74) 2.429 ms 4.358 ms 2.866 ms
4 140.113.0.161 (140.113.0.161) 4.497 ms 6.394 ms 4.826 ms

>> arp -a
? (172.18.80.9) at b4:52:7d:7d:15:46 on en0 [ethernet]
? (172.18.80.12) at f4:f1:5a:d5:80:76 on en0 [ethernet]
? (172.18.80.31) at 84:0:d2:52:20:a5 on en0 [ethernet]
? (172.18.80.49) at d0:51:62:2b:2c:64 on en0 [ethernet]
? (172.18.80.69) at 1c:b0:94:88:68:a7 on en0 [ethernet]
? (172.18.80.91) at d0:51:62:3a:f6:ff on en0 [ethernet]
? (172.18.80.110) at e8:99:c4:ba:41:1 on en0 [ethernet]
? (172.18.80.113) at 4c:21:d0:43:3a:56 on en0 [ethernet]
? (172.18.80.117) at 1c:7b:21:7a:bf:33 on en0 [ethernet]
? (172.18.80.119) at c:74:c2:4d:6e:2b on en0 [ethernet]
? (172.18.80.122) at bc:85:56:2d:cb:f on en0 [ethernet]
? (172.18.80.124) at 44:d8:84:56:72:3b on en0 [ethernet]
? (172.18.80.125) at b4:52:7d:79:71:78 on en0 [ethernet]
? (172.18.80.129) at 20:7d:74:1a:95:81 on en0 [ethernet]
? (172.18.80.132) at d0:51:62:10:9c:84 on en0 [ethernet]
? (172.18.80.134) at b4:52:7e:72:7:74 on en0 [ethernet]
? (172.18.80.135) at dc:9b:9c:a4:2a:61 on en0 [ethernet]
? (172.18.80.136) at 30:f7:c5:2c:8d:48 on en0 [ethernet]
? (172.18.80.141) at 18:e7:f4:80:88:50 on en0 [ethernet]
? (172.18.80.245) at 0:eb:2d:e3:9c:21 on en0 [ethernet]
? (172.18.81.41) at f4:f1:5a:91:39:88 on en0 [ethernet]
? (172.18.81.61) at 18:e7:f4:9:61:4 on en0 [ethernet]
? (172.18.82.21) at 4c:8d:79:a4:21:4f on en0 [ethernet]
? (172.18.82.48) at 1c:7b:21:c2:1d:80 on en0 [ethernet]
? (172.18.82.168) at 78:6c:1c:d6:3c:7f on en0 [ethernet]
? (172.18.82.255) at 34:c0:59:a0:48:dc on en0 [ethernet]
? (172.18.83.150) at 84:38:35:a6:62:58 on en0 [ethernet]
? (172.18.84.102) at 1c:7b:21:61:2e:69 on en0 [ethernet]
? (172.18.84.178) at 90:b9:31:d:ee:ad on en0 [ethernet]
? (172.18.85.12) at e0:f5:c6:70:9e:5c on en0 [ethernet]
? (172.18.85.127) at c8:6f:1d:1e:ec:12 on en0 [ethernet]
? (172.18.87.254) at a8:d0:e5:a4:38:10 on en0 [ethernet]