急！！Linux不定期网络断开！！

cctcc

Aug 25 15:47:25 localhost kernel: e1000: eth0: e1000_watchdog: NIC Link is Down
Aug 25 15:47:26 localhost kernel: e1000: eth0: e1000_watchdog: NIC Link is Up 100 Mbps Full Duplex
Aug 25 15:49:34 localhost unix_chkpwd[7262]: check pass; user unknown
Aug 25 15:49:34 localhost vsftpd(pam_unix)[7260]: authentication failure; logname= uid=0 euid=0 tty= ruser= rhost=210.5.1.17
Aug 25 15:50:01 localhost crond(pam_unix)[7264]: session opened for user root by (uid=0)
Aug 25 15:50:01 localhost crond(pam_unix)[7263]: session opened for user root by (uid=0)
Aug 25 15:50:01 localhost crond(pam_unix)[7264]: session closed for user root
Aug 25 15:50:01 localhost crond(pam_unix)[7263]: session closed for user root
Aug 25 15:54:19 localhost kernel: e1000: eth0: e1000_watchdog: NIC Link is Down
Aug 25 15:54:21 localhost kernel: e1000: eth0: e1000_watchdog: NIC Link is Up 100 Mbps Full Duplex
Aug 25 16:02:19 localhost kernel: e1000: eth0: e1000_watchdog: NIC Link is Down

结果网卡到16:02:19Down了之后就没起来！只好重启服务器。这种情况是每隔5、6天出现　一次（网络断开无法连接）

系统装的是：Enterprise AS 4
内核： 2.6.9-5.ELsmp
使用的DELL的PowerEdge 1800　集成的千兆网卡.

真不知该怎么办了！！请求救高手指点迷津！

再此先谢过了。