[root@Cloud root]# ifconfig eth0
eth0 Link encap:Ethernet HWaddr 00:A0:CC7:62:81

inet addr:210.31.34.2 Bcast:210.31.47.255 Mask:255.255.240.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:13716 errors:0 dropped:0 overruns:0 frame:0
TX packets:1349 errors:0 dropped:0 overruns:0 carrier:0
collisions:416 txqueuelen:1000
RX bytes:2350481 (2.2 Mb) TX bytes:207707 (202.8 Kb)
Interrupt:5 Base address:0xcc00
[root@Cloud root]# arp -s 210.31.34.2 00:A0:CC7:62:81

SIOCSARP: Invalid argument
为什么会这样啊?搞不懂?