做挂载网络文件系统实验碰到问题

按照贵公司手册在设置了cigc和boa，并以nfs方式启动开发板后出现以下错误，请问怎么解决呢？
TCP cubic registered
RPC: Registered udp transport module.
RPC: Registered tcp transport module.
lib80211: common routines for IEEE802.11 drivers
s3c2410-rtc s3c2410-rtc: setting system clock to 2010-01-17 23:21:50 UTC (126377
0510)
eth0: link down
Sending DHCP requests .<6>eth0: link up, 100Mbps, full-duplex, lpa 0xCDE1
..... timed out!
IP-Config: Retrying forever (NFS root)...
eth0: link down
Sending DHCP requests .<6>eth0: link up, 100Mbps, full-duplex, lpa 0xCDE1
..... timed out!
IP-Config: Retrying forever (NFS root)...
eth0: link down
Sending DHCP requests .<6>eth0: link up, 100Mbps, full-duplex, lpa 0xCDE1
..... timed out!
IP-Config: Retrying forever (NFS root)...
eth0: link down
    一直死在这里，进不了命令行，请问是什么问题呢？？？

eth0: link down，这个地方显示你的网络在物理上没有连通。