pppoe问题

刚开机时能正常使用pppoe上网，可是没有多久，就会断线，此时在NetworkManagement Applet中找不到pppoe或者eth0的选项， 命令行显示如下
[03/25/2014,16:37:08@~]$ plog
Mar 25 16:36:13 debian pppd[2068]: error sending pppoe packet: No such device or address
Mar 25 16:36:33 debian pppd[2068]: Timeout waiting for PADO packets
Mar 25 16:36:33 debian pppd[2068]: Unable to complete PPPoE Discovery
Mar 25 16:37:03 debian pppd[2068]: error sending pppoe packet: No such device or address
Mar 25 16:37:03 debian pppd[2068]: error receiving pppoe packet: Network is down
Mar 25 16:37:08 debian pppd[2068]: error sending pppoe packet: No such device or address
Mar 25 16:37:08 debian pppd[4607]: Plugin rp-pppoe.so loaded.
Mar 25 16:37:08 debian pppd[4608]: pppd 2.4.5 started by zhimath, uid 1001
Mar 25 16:37:08 debian pppd[4608]: error sending pppoe packet: No such device or address
Mar 25 16:37:08 debian pppd[4608]: error receiving pppoe packet: Network is down
[03/25/2014,16:37:10@~]$


[03/25/2014,16:42:07@~/Desktop]$ plog
Mar 25 16:42:07 debian pppd[5371]: Connected to 00:1e:73:9a:c8:40 via interface eth0
Mar 25 16:42:07 debian pppd[5371]: Using interface ppp3
Mar 25 16:42:07 debian pppd[5371]: Connect: ppp3 <--> eth0
Mar 25 16:42:07 debian pppd[5371]: CHAP authentication failed: M-4M-mM-NM-sM-BM-k110:M-SM-CM-;M-'M-TM-ZM-OM-_M-JM-}M-OM-^M-VM-F
Mar 25 16:42:07 debian pppd[5371]: CHAP authentication failed
Mar 25 16:42:07 debian pppd[5371]: Connection terminated.

此时需要重启后又可以用pppoe上网，约一小时后又出现类似问题。

请问如何解决？