VPS can't connect to Internet "Unknown Host"

Hello again, today i want to show you to fix some little problem that may occur on your VPS, i experience it today, while i installing package from yum or in other word officially apps for Centos 6 64Bit, everything is fine, i can host my website using wordpress, connect SSH, surfing with VPN, etc, no problem at all, this time i using VPS provided by EthernetServer.com for review purpose with Intel(R) Xeon(R) CPU E3-1240 v3 @ 3.40GHz as CPU - 2GB Ram - 100GB SSD - and 2TB Bandwidth (check limited offer here).

And, i start reboot my VPS, nothing strange happened or maybe i didn't realized it, i try run VNC and connect to KDE from windows, and tada...

"The connection was refused by the host computer"

And i try start my vncserver from terminal, i type vncserver from terminal, it won't start.

I think my VPS can't connect to Internet, so to make sure, not guessing, i try simple thing, i type :

ping www.google.com

"unknown host"

Yes indeed, there are conflict in network, so it block each other, maybe when you installing some package, you don't realized you already create that conflict.

Fisrt to make sure again i type :

chkconfig --list | grep -Ei 'network|wpa'

network         0:off   1:off   2:on    3:on    4:on    5:on    6:off
NetworkManager  0:off   1:off   2:on    3:on    4:on    5:on    6:off
wpa_supplicant  0:off   1:off   2:off   3:off   4:off   5:off   6:off

That's the problem, 2 network manage in one system, so try remove NetworkManager, type :

yum remove NetworkManager

Then restart or reboot your VPS, try ping first.

ping www.google.com

64 bytes from yyz08s14-in-f16.1e100.net (74.125.226.144): icmp_seq=1 ttl=54 time=2.37 ms
64 bytes from yyz08s14-in-f16.1e100.net (74.125.226.144): icmp_seq=2 ttl=54 time=2.33 ms

it success, then i try connect to KDE using VNC in windows 7

"The connection was refused by the host computer"

this occur because vncserver is not started, try start it by type :

vncserver

New 'server.angelimus.com:1 (root)' desktop is server.angelimus.com:1

Starting applications specified in /root/.vnc/xstartup
Log file is /root/.vnc/server.angelimus.com:1.log

IT's DONE, PROBLEM SOLVED, but what cause that matter? so i reinstall my VPS, and try install package one by one, after installing i do reboot, and then ping, no problem so far, until i install KDE (Tutorial INSTALL KDE click here), after i reboot, i can't ping Google.

So i assume, that source of problem is from KDE, but from previous tutorial that i using another VPS Host, this kind of problem is not exist. Maybe i just unlucky or something passed by me.

Hope my experience can help you solve problem like this.