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]

Sharing IPMI IP with the host

以下連結的網頁是針對 IPMI 板子與 host 共用 IP 的問題所作的討論：
http://serverfault.com/questions/259792/how-does-ipmi-sideband-share-the-ethernet-port-with-the-host

我在此稍微作筆記、翻譯

• Sharing Ethernet means that LAN1 appears to have 2 MAC addresses(the IPMI interface, the standard Broadcom NIC)
• 公用同一條網路線表示LAN1會有兩個對應到的MAC位址（IPMI和原本的網路卡）
• Traffic to the IPMI interface is magically intercepted below the operating system level and never seen by whatever OS is running.
• 原本到 IPMI 介面的流量會跑到作業系統底下，而不論使用什麼作業系統都將無法看到

Downsides for sharing the IP for IPMI and OS host

• It's particularly difficult to partition the IPMI interface onto a separate subnet in a secure manner.
• 很難做到將兩者分開成不同子網路以保證安全
• The latest IPMI cards now support assigning a VLAN to the IPMI NIC, so you can get some semblance of separation - but the underlying OS could always sniff the traffic for that VLAN.
• 最新的IPMI卡可以支持把VLAN轉到IPMI NIC的功能，所以你可以得到一個「看似」兩者區分開來的樣子，但是OS仍然可以監視到該通訊流
• Older BMC controllers don't allow changing the VLAN at all, although tools like ipmitool or ipmicfg will ostensibly let you change it, it just doesn't work.
• 比較舊的BMC控制器不允許你更便VLAN，雖然有像是ipmitool或ipmicfg等工具，但是就是辦不到
• You're centralizing your failure points on the system. Doing configuration on a switch and manage to cut yourself off somehow? And, you've now cut off the primary network connection to your server AND the backup via IPMI. NIC hardware fail? Same problem,
• 你把所有可能失敗的地方都集中在系統，要怎麼設定一個開關，然後要他關掉自己？你關掉最重要的到伺服器的網路連線和透過IPMI備份的機制。至於NIC硬體問題也會遇到一樣的狀況

照這份文章的解釋，不建議我們設法把 IPMI 和 host IP共用。