CentOS - Sep 2016 - Network manager cannot connet to the Internet

Dear all,
I find out of a sudden my?Network?manager cannot connect to the Internet. My OS
is Centos 6.7, and the version of?Network?manager is Applet 0.8.1. When clinking
the ?Network?manager icon at the upper right conner at the Desktop of my
compuer, I can see in the?pop-up?manu that there are two network ?cards (Intel
82573E Gigabit Ethernet Controller (Copper) and Intel 82573L Gigabit Ethernet
Controller)?but?only one link (System eth1) available. Usually when clicking the
"System eth1" the Internet connection would be established. However
from this morning?clicking the "System eth1" only gives connect
failure information. I don't know whether this is caused by intalling a
large software package (ambertool 16 ) which requires many updates in my system
yesterday. ? ?But when I give "ifconfig" command in a gnome terminal,
the output information seems to be correct:

[sunyp at localhost?Desktop]$?ifconfig???
eth0??????Link?encap:Ethernet??HWaddr?00:25:90:72:E2:86??
??????????UP?BROADCAST?MULTICAST??MTU:1500??Metric:1
??????????RX?packets:0?errors:0?dropped:0?overruns:0?frame:0
??????????TX?packets:0?errors:0?dropped:0?overruns:0?carrier:0
??????????collisions:0?txqueuelen:1000?
??????????RX?bytes:0?(0.0?b)??TX?bytes:0?(0.0?b)
??????????Interrupt:16?Memory:faee0000-faf00000?

eth1??????Link?encap:Ethernet??HWaddr?00:25:90:72:E2:87??
??????????inet6?addr:?fe80::225:90ff:fe72:e287/64?Scope:Link
??????????UP?BROADCAST?RUNNING?MULTICAST??MTU:1500??Metric:1
??????????RX?packets:49?errors:0?dropped:0?overruns:0?frame:0
??????????TX?packets:11?errors:0?dropped:0?overruns:0?carrier:0
??????????collisions:0?txqueuelen:1000?
??????????RX?bytes:16386?(16.0?KiB)??TX?bytes:3038?(2.9?KiB)
??????????Interrupt:17?Memory:fafe0000-fb000000?

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:65536??Metric:1
??????????RX?packets:90?errors:0?dropped:0?overruns:0?frame:0
??????????TX?packets:90?errors:0?dropped:0?overruns:0?carrier:0
??????????collisions:0?txqueuelen:0?
??????????RX?bytes:6737?(6.5?KiB)??TX?bytes:6737?(6.5?KiB)

What I can do now? Could anyone help me with this problem?
Best regards.
Yeping Sun

What is the output of ip route show, can you ping your gateway, first see
if you can ping your default gateway and if you can't you will have to
check the device that your are connecting to.

-- 
Kind Regards
Earl Ramirez

Hi,?Earl,
Thank you very much for your prompt response.There is no output for "ip
route"I don't know what is my default gateway and how to check it??And
how to?check?the?device?that I am connecting?to?
Best regards.
Yeping------------------------------------------------------------------From:Earl
A Ramirez <earlaramirez at gmail.com>Time:2016 Sep 3 (Sat) 18:38To:CentOS
mailing list <centos at centos.org>Subject:Re: [CentOS] Network manager
cannot connet to the Internet
What?is?the?output?of?ip?route?show,?can?you?ping?your?gateway,?first?see
if?you?can?ping?your?default?gateway?and?if?you?can't?you?will?have?to
check?the?device?that?your?are?connecting?to.

--?
Kind?Regards
Earl?Ramirez
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On 09/03/2016 03:08 AM, sunyeping wrote:
> But when I give "ifconfig" command in a gnome terminal, the
output information seems to be correct:
>
> [sunyp at localhost Desktop]$ ifconfig
> ...
> eth1      Link encap:Ethernet  HWaddr 00:25:90:72:E2:87
>            inet6 addr: fe80::225:90ff:fe72:e287/64 Scope:Link
>            UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
>            RX packets:49 errors:0 dropped:0 overruns:0 frame:0
>            TX packets:11 errors:0 dropped:0 overruns:0 carrier:0
>            collisions:0 txqueuelen:1000
>            RX bytes:16386 (16.0 KiB)  TX bytes:3038 (2.9 KiB)
>            Interrupt:17 Memory:fafe0000-fb000000

You don't have any valid IPv4 or IPv6 addresses.  Normally those things 
are provided by your router.  Check your cabling first. Then check your 
router's logs to see if it's getting DHCP requests from your desktop.