CentOS Networking with V Box

Kevin Fries kevin at fries-biro.com
Tue Feb 3 23:47:55 MST 2015 

If your interface has no IP, you can't communicate out to anywhere, and we
are back to the conversation about starting and enabling your network
service.
On Feb 3, 2015 11:45 PM, "Michael Torres" <matorres124 at gmail.com> wrote:

> thats the point.... I dont have an IP address...there is nothing that I
> put to scan it.  My NIC was allowing it when I was at Starbucks..  That is
> why I think its my router, as such isnt the router that assigns IP address
> to the network when using DHCP?
>
> On Tue, Feb 3, 2015 at 11:39 PM, Kevin Fries <kevin at fries-biro.com> wrote:
>
>> Ok, down to two possibilities.
>>
>> Nmap is a scanner.  It is trying to identify your VM and probe for open
>> ports.
>>
>> When you scanned by name... it did not understand that name.  Your router
>> is external to all of this, and should not be involved at all.
>>
>> Try nmap by IP address.
>>
>> If that still results in nothing, add a virtual network via VMware or
>> VBox.  Next add a new virtual network adapter to your VM, and connect it to
>> the new network.  This should be a private network between host and
>> client.  Config your interface in the VM.  This will resolve your problem.
>> In this case, your NIC is not allowing traffic to go out, then back in to
>> itself.  The traffic is almost certainly not going to your router then back.
>>
>> HTH
>> Kevin
>> On Feb 3, 2015 10:41 PM, "Michael Torres" <matorres124 at gmail.com> wrote:
>>
>>> netstat -plant
>>>
>>> liastening on ports 25 and 22 both for IPv4 nad IPv6
>>>
>>> Result from the nmap(windows version)
>>> Starting Nmap 6.47 ( http://nmap.org ) at 2015-02-03 22:36 US Mountain
>>> Standard Time
>>>
>>> NSE: Loaded 118 scripts for scanning.
>>>
>>> NSE: Script Pre-scanning.
>>>
>>> NSE: Script Post-scanning.
>>>
>>> Read data files from: C:\Program Files (x86)\Nmap
>>>
>>> Nmap done: 0 IP addresses (0 hosts up) scanned in 4.20 seconds
>>>
>>>            Raw packets sent: 0 (0B) | Rcvd: 0 (0B)
>>>
>>> Failed to resolve "devserver".
>>>
>>> WARNING: No targets were specified, so 0 hosts scanned.
>>>
>>> I would ahave asusmed the the above results as the dhcp server is not
>>> generating a IPv4 address
>>>
>>>
>>> so...
>>>
>>>   1) The netstat does not show the binding to port 21... this means SSHD
>>> did not start.
>>>
>>> I am guessing port 22 is OK
>>>
>>>   2) netstat shows SSHD, but the firewall is not allowing it.  Open the
>>> firewall
>>>
>>> Firewall is already disabled
>>>
>>>   3) netstat shows SSHD, the firewall is open, but you still don't see
>>> the port open via nmap.
>>>
>>>     3a) if you see other ports open, I would look at the Windows firewall
>>>
>>> Windows firewall allowed it on a Public network (startbuck), so why not
>>> allow it at my home
>>>
>>>     3b) If you don't see any ports open, you have two options here.
>>>
>>>        3b1) Make sure your NIC (from the Windows side) is in promiscuous
>>> mode.
>>>
>>> dont know how to do that.
>>>
>>>        3b2) If it is already in promiscuous mode, then this may not work
>>> in this configuration.  In this case, try adding a private network on a
>>> second NIC, and communicate with the VM over that.
>>> Ill try to connect to my ethernet adpater and see if that is it, maybe
>>> its my wireless adapter....
>>>
>>> Mike
>>>
>>>
>>> On Tue, Feb 3, 2015 at 10:22 PM, Kevin Fries <kevin at fries-biro.com>
>>> wrote:
>>>
>>>> Ok, sorry, I misunderstood.
>>>>
>>>> Nmap could be your friend here.  Install it on your Windows machine.
>>>> It will install the graphical tool automatically in Windows.  Point this at
>>>> your VM, and do a "intense scan"
>>>>
>>>> Next, on the Linux VM, do a
>>>>   # netstat -plant
>>>>
>>>> Zenmap/Nmap will tell you what ports it can see open from its side of
>>>> the link.  The netstat command will tell you which ports are opened by
>>>> running software.
>>>>
>>>> Lastly, on the Linux VM, do a
>>>>    # ip tables -L
>>>>
>>>> This will tell you which ports the firewall will allow.
>>>>
>>>> Now, you have a few possibilities:
>>>>
>>>>   1) The netstat does not show the binding to port 21... this means
>>>> SSHD did not start.
>>>>
>>>>   2) netstat shows SSHD, but the firewall is not allowing it.  Open the
>>>> firewall
>>>>
>>>>   3) netstat shows SSHD, the firewall is open, but you still don't see
>>>> the port open via nmap.
>>>>
>>>>     3a) if you see other ports open, I would look at the Windows
>>>> firewall
>>>>
>>>>     3b) If you don't see any ports open, you have two options here.
>>>>
>>>>        3b1) Make sure your NIC (from the Windows side) is in
>>>> promiscuous mode.
>>>>
>>>>        3b2) If it is already in promiscuous mode, then this may not
>>>> work in this configuration.  In this case, try adding a private network on
>>>> a second NIC, and communicate with the VM over that.
>>>>
>>>> Let me how it goes.
>>>>
>>>> Kevin
>>>> On Feb 3, 2015 9:58 PM, "Michael Torres" <matorres124 at gmail.com> wrote:
>>>>
>>>>> Well, no,  I didnt issue any commands other than
>>>>> /path/to/network/script/network start /path/to/network/script/network stop
>>>>> and the commands to disable firewall/SELINUX
>>>>>
>>>>> I know I didnt use any systemctrl commands., but I tried to run the
>>>>> commands that you just provided and nothing happened.  I should probably
>>>>> say that I know that IPv6 is enalbed and have network connection to the net
>>>>> work and I can ping yahoo.com etc.....  I just cant SSH(putty) to the
>>>>> server.
>>>>>
>>>>> This all leads me to beleive that there is a configuration in my
>>>>> router that is not allowing me to get a IPv4 address. Does the default
>>>>> gateway have to be a certain number?  I have manually configured that IP on
>>>>> my router a long  time ago, but even then I had Bridged networking working
>>>>> correctly.
>>>>>
>>>>> Mike
>>>>>
>>>>>
>>>>>
>>>>> On Tue, Feb 3, 2015 at 9:48 PM, Kevin Fries <kevin at fries-biro.com>
>>>>> wrote:
>>>>>
>>>>>> Your network is probably not getting started.  The enp0p3 is the name
>>>>>> of an interface started almost definantly  by systemd, not the old RHEL
>>>>>> way.  This is likely why the networking-scripts didn't work.
>>>>>>
>>>>>> When you were at Starbucks, you likely did a systemctl start on the
>>>>>> interface.  Look in your history for it.  If you find it, issue the same
>>>>>> command again.  If your interface comes up correctly,  reissue the command
>>>>>> once again, substituting enable for start.  This second command is similar
>>>>>> to a chkconfig command.
>>>>>>
>>>>>> Let me know how that works.
>>>>>>
>>>>>> Kevin
>>>>>> On Feb 3, 2015 9:13 PM, "Michael Torres" <matorres124 at gmail.com>
>>>>>> wrote:
>>>>>>
>>>>>>> The result of that command is:
>>>>>>>
>>>>>>> 0 loaded units listed
>>>>>>>
>>>>>>>
>>>>>>> So I ran a what it suggested: systemctl list-unit-files
>>>>>>> majority of everything says "static"  but some are "enabled" or
>>>>>>> "disabled"
>>>>>>>
>>>>>>> again, because  I cannot copy or capture a screen shot, is there a
>>>>>>> specific list item that you need to see?"
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> On Tue, Feb 3, 2015 at 8:44 PM, Kevin Fries <kevin at fries-biro.com>
>>>>>>> wrote:
>>>>>>>
>>>>>>>> Do a
>>>>>>>>
>>>>>>>> # systemctl --failed
>>>>>>>>
>>>>>>>> And post the results
>>>>>>>>
>>>>>>>> Kevin
>>>>>>>> On Feb 3, 2015 8:37 PM, "Michael Torres" <matorres124 at gmail.com>
>>>>>>>> wrote:
>>>>>>>>
>>>>>>>>> Arrghh....yes its configured.  But I am having an issue getting
>>>>>>>>> the cat /etc/sysconfig/network-script/ifcfg-enp0s3..........because I cant
>>>>>>>>> connect,  I cant ssh in to use outty so I can copy using my mouse.  I tried
>>>>>>>>> taking a screen shot, but VBox for some reason wont display on on the
>>>>>>>>> "print screen"command.
>>>>>>>>>
>>>>>>>>> is there a particular setting you are looking for?  again, the
>>>>>>>>> file is configured and it is reading it.
>>>>>>>>>
>>>>>>>>> Mike
>>>>>>>>>
>>>>>>>>> On Tue, Feb 3, 2015 at 8:15 PM, Stephen M <smelheim85 at gmail.com>
>>>>>>>>> wrote:
>>>>>>>>>
>>>>>>>>>> I don't remember if this is a problem in centos 7 as it was in
>>>>>>>>>> 6.  But check to make sure the eth0 is configured.   But yes a print out of
>>>>>>>>>> ifconfig inside vox would be great.
>>>>>>>>>> On Feb 3, 2015 8:07 PM, "Michael Torres" <matorres124 at gmail.com>
>>>>>>>>>> wrote:
>>>>>>>>>>
>>>>>>>>>>> Hello all,
>>>>>>>>>>>
>>>>>>>>>>> I have an problem that  I cannot seem to figure out.....
>>>>>>>>>>>
>>>>>>>>>>> I am trying to use "Bridged" networking in Virtual Box to a
>>>>>>>>>>> CentOS 7 minimum install distro that I want to use for my development
>>>>>>>>>>> server.
>>>>>>>>>>>
>>>>>>>>>>> I have used Bridged networking in the past and never had any
>>>>>>>>>>> issues but that was with older versions of CentOS
>>>>>>>>>>>
>>>>>>>>>>> The issue....  DHCP will not assign a IPv4 address to the server.
>>>>>>>>>>>
>>>>>>>>>>> Here is the weird part...  I was at startbucks and actually got
>>>>>>>>>>> it to work! (Please, hold the "Just use it at starbucks then" comments..I
>>>>>>>>>>> know....)
>>>>>>>>>>>
>>>>>>>>>>> Here is the process I used...
>>>>>>>>>>>
>>>>>>>>>>> -Installed a fresh CentOS 7 on VBox
>>>>>>>>>>> -While on NAT,  I performed "yum update" so my server was fresh
>>>>>>>>>>> with the latest
>>>>>>>>>>> -Disabled SELinux
>>>>>>>>>>> -Disabled the Firewall
>>>>>>>>>>> -Shut down server to reconfigure the adapter to "Bridged"
>>>>>>>>>>> -used adapter type of "Intel Pro 1000 MT Desktop (82540EM)"
>>>>>>>>>>> -set it to "Promiscuous Mode"
>>>>>>>>>>> -restart the server
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>> Again, at Starbucks it assigned a IP address, so this leads me
>>>>>>>>>>> to believe that the issue is with a configuration on my router.
>>>>>>>>>>>
>>>>>>>>>>> I am not very good at networking, so any help would be
>>>>>>>>>>> appreciated.
>>>>>>>>>>>
>>>>>>>>>>> If you need error messages or other output, let me know (and
>>>>>>>>>>> possibly the command as I don't know networking that well other than
>>>>>>>>>>> "ifconfig")
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>> Mike
>>>>>>>>>>>
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