ifconig内容：
eth0 Link encap:Ethernet HWaddr 00:11:5B:1D:1B:A3
inet addr:192.168.1.2 Bcast:192.168.1.255 Mask:255.255.255.0
inet6 addr: fe80::211:5bff:fe1d:1ba3/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:68 errors:0 dropped:0 overruns:0 frame:0
TX packets:84 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:6589 (6.4 KiB) TX bytes:7191 (7.0 KiB)
Interrupt:185 Base address:0xc000
lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
inet6 addr: ::1/128 Scope:Host
UP LOOPBACK RUNNING MTU:16436 Metric:1
RX packets:2 errors:0 dropped:0 overruns:0 frame:0
TX packets:2 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:100 (100.0 b) TX bytes:100 (100.0 b)
ppp0 Link encap:Point-to-Point Protocol
inet addr:221.217.90.7 P-t-P:61.149.112.1 Mask:255.255.255.255
UP POINTOPOINT RUNNING NOARP MULTICAST MTU:1492 Metric:1
RX packets:36 errors:0 dropped:0 overruns:0 frame:0
TX packets:36 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:3
RX bytes:3267 (3.1 KiB) TX bytes:2675 (2.6 KiB)
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/etc/network/interface内容：
auto lo
iface lo inet loopback
auto eth0
iface eth0 inet dhcp
auto eth1
iface eth1 inet dhcp
auto eth2
iface eth2 inet dhcp
auto ath0
iface ath0 inet dhcp
auto wlan0
iface wlan0 inet dhcp
auto dsl-provider
iface dsl-provider inet ppp
provider dsl-provider
pre-up /sbin/ifconfig eth0 up # line maintained by pppoeconf
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运行sudo pppoeconf 检测网卡eth0时无法连接（昨天还能用呢）┤ NOT CONNECTED ├
Sorry, I scanned 1 interface, but the Access
Concentrator of your provider did not respond. Please
check your network and modem cables. Another reason
for the scan failure may also be another running pppoe
process which controls the modem.
最后是日志/var/log/messages内容：
Dec 26 09:30:05 zhangyue-desktop pppoe-discovery: Timeout waiting for PADO packets