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Thread: Virtual Networking -some Basics - All OS

  1. #11

    Default Re: Virtual Networking -some Basics - All OS

    Update:
    This doc is better:
    https://wiki.libvirt.org/page/VirtualNetworking
    I must correct myself: I did not try pinging from other PCs in physical LAN to virtual guest, only from openSUSE host.

    Still doc insist in the fact libvirt creates a "default" virtual network (in NAT mode) when installed and started. This was clearly not my case. Could it be because I accepted Yast's advise of creating bridges back when installing KVM stuff?

    Yet, still in need of help for the other doubts:

    Why still 2 virbr0 devices?
    When configuring the bridge in virt-manager I left forward to "any physical device". Is it actually taking any *working* physical device that it detects, or what?
    Is brctl really the only way to disable STP on bridges?

  2. #12
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    Default Re: Virtual Networking -some Basics - All OS

    Quote Originally Posted by F_style View Post
    Update:
    This doc is better:
    https://wiki.libvirt.org/page/VirtualNetworking
    I must correct myself: I did not try pinging from other PCs in physical LAN to virtual guest, only from openSUSE host.

    Still doc insist in the fact libvirt creates a "default" virtual network (in NAT mode) when installed and started. This was clearly not my case. Could it be because I accepted Yast's advise of creating bridges back when installing KVM stuff?

    Yet, still in need of help for the other doubts:

    Why still 2 virbr0 devices?
    When configuring the bridge in virt-manager I left forward to "any physical device". Is it actually taking any *working* physical device that it detects, or what?
    Is brctl really the only way to disable STP on bridges?
    I haven't deployed a brand new 42.3 KVM Host as of yet to know for sure if anything has changed (intentionally or not).
    In any case, if all you notice awry is a missing NAT network, I'd consider that minor, and practically trivial to resolve although keep in mind that the NetworkID you set up may not be the same as what should have been configured by default. In your case, unless you re-built from scratch after your admitted mis-steps installing, your system shouldn't be considered typical. Creating bridge devices during the YaST setup no matter how and what you did would have <no effect> whatsoever on libvirt created bridge devices. At least, I can't see any possible conflict.

    In what you posted, virbr0 is mapped to multiple interface objects.
    In your specific case(not necessarily applicable to others) I don't see that you should see any unusual functionality, and your multiple entries are related to how the STP (spanning tree protocol) works.
    In general, you <never> want to disable implementing the STP, because it provides safeguards against various misconfigurations. You can read various articles about the STP, but as long as you don't have a special need to inrwnrionLLY configure spanning multiple network interfaces and keep your bridge devices accordingly very simple(eg bind to physical interfaces and never or rarely other bridge devices), then you don't have to learn very much about STP, just accept how it's configured automatically.

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  3. #13

    Default Re: Virtual Networking -some Basics - All OS

    Got a garbage PC only for a day, just to get rid of certain doubts no one here has ever been able to solve.

    Clean-installed Leap 42.3 **3 D***ED times**:

    --Installed KVM again through Yast and accepting its nasty bridges. No mistake: it always creates 2 br's. So anyway had to switch to Wicked, and immediately did the test of deleting br0 -the one with nothing- and leaving br1 -the one with dhcp and eth0 slaved-. Again used the Linux liveCD for a test virtual guest, for which I certainly used br1.
    Result: worked pretty good just like Proxmox bridged style.
    Conclusion: only one br interface is needed, not two! D**n Yast...

    --Installed KVM yet again through Yast, but rejecting bridge offering.

    --Installed KVM with "zypper in -t pattern kvm_server" and enabled libvirtd service.

    Result of last 2 cases: no virtual networks at all created out of the box; I had to manually create one.
    This piece of....... text is false:
    "A standard libvirt installation on openSUSE Leap already comes with a predefined virtual network providing DHCP server and network address translation (NAT) named "default"."
    Unfortunately totally false...

    During last case I did some few last tests, first of all going back to Network manager.

    A bridge can also be created through Settings > Network > wired network properties. Problem is virt-installer/virt-manager never recognizes it. Perhaps it's true what was mentioned in a past thread: virt-manager is designed to only work with Wicked regarding bridges.

    Seemingly virt-manager's virtual networks are designed to never work in same network segment as host's currently used interface; virtual guests get external access either through NAT or routed modes, but always in a different network segment.
    In NAT mode virtual guests can see everything outside, but can only be seen by host itself and other guests under same virtual network. No PCs in physical LAN can see virtual guests due to iptables rules in virtual network.

    Just curiosity, does anyone have idea of how one could make an "external" PC in LAN communicate with virtual guests? Would it be through iptable rule modifying?
    What's depicted here certainly looks more lika a "hack"...

  4. #14
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    Default Re: Virtual Networking -some Basics - All OS

    Quote Originally Posted by F_style View Post
    Got a garbage PC only for a day, just to get rid of certain doubts no one here has ever been able to solve.

    Clean-installed Leap 42.3 **3 D***ED times**:

    --Installed KVM again through Yast and accepting its nasty bridges. No mistake: it always creates 2 br's. So anyway had to switch to Wicked, and immediately did the test of deleting br0 -the one with nothing- and leaving br1 -the one with dhcp and eth0 slaved-. Again used the Linux liveCD for a test virtual guest, for which I certainly used br1.
    Result: worked pretty good just like Proxmox bridged style.
    Conclusion: only one br interface is needed, not two! D**n Yast...

    --Installed KVM yet again through Yast, but rejecting bridge offering.

    --Installed KVM with "zypper in -t pattern kvm_server" and enabled libvirtd service.

    Result of last 2 cases: no virtual networks at all created out of the box; I had to manually create one.
    This piece of....... text is false:
    "A standard libvirt installation on openSUSE Leap already comes with a predefined virtual network providing DHCP server and network address translation (NAT) named "default"."
    Unfortunately totally false...

    During last case I did some few last tests, first of all going back to Network manager.

    A bridge can also be created through Settings > Network > wired network properties. Problem is virt-installer/virt-manager never recognizes it. Perhaps it's true what was mentioned in a past thread: virt-manager is designed to only work with Wicked regarding bridges.

    Seemingly virt-manager's virtual networks are designed to never work in same network segment as host's currently used interface; virtual guests get external access either through NAT or routed modes, but always in a different network segment.
    In NAT mode virtual guests can see everything outside, but can only be seen by host itself and other guests under same virtual network. No PCs in physical LAN can see virtual guests due to iptables rules in virtual network.

    Just curiosity, does anyone have idea of how one could make an "external" PC in LAN communicate with virtual guests? Would it be through iptable rule modifying?
    What's depicted here certainly looks more lika a "hack"...
    Hi
    Maybe it creates two bridges due to having one wireless and one etherent. Now if you look at the bridges created via YaST -> Network Settings, select bridges and edit, you will see they may not be associated to an interface. Again you can go in and set this up how you want (which is as it should be).

    The system I used (running Tumbleweed at the moment, no vm's) for vm's has three (3) ethernet interfaces and bridged (br0, br1 and br2) and connected direct to the guest as a physical interface (static ip's), the wireless interface is used for management so no issues with external pc's in local network contacting guest vm's.

    You might want to try gnome boxes as AFAIK this interfaces direct with NetworkManager, but has limited options (but does use spice).
    Cheers Malcolm °¿° SUSE Knowledge Partner (Linux Counter #276890)
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  5. #15
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    Default Re: Virtual Networking -some Basics - All OS

    Since time immemorial,
    br0 has always been created by YaST in a "bridging mode" configuration that exposes the physical LAN to the Guest(and vice versa).
    This means for example that if you configure the Guest network settings as a DHCP client, it will contact the same DHCP Server physical machines in the LAN also use, and the Guest will be assigned an IP address with the same NetworkID as every other physical machine in the LAN. This also means that remote machines can find and communicate with the Guest, so the Guest can itself be configured to provide network services... For example, being configured as a Network File Server serving network shares.

    If a br1 is created by YaST, that would be new and worth investigating. As of today, it's not possible to use YaST to manually create a bridging device that supports NAT, you'd have to first create it, then modify its configuration likely with a text editor. Of course, something like this could be pre-configured for special installation when YaST installs virtualization, but I haven't seen it prior to 42.3 (and I haven't verified this happens in 42.3).

    On the other hand, as the documentation says when you install libvirt (typically using YaST virtuallization install) you're supposed to have a virbr (not br) named device that is set up as a NAT device.

    If you install KVM without libvirt, then you should know that no current openSUSE or SUSE documentation will describe your setup or how to use and manage your virtualization. You can still use an alternative to libvirt(eg Vagrant) or use KVM or QEMU command lines to do everything you need to do, though I'd recommend the official KVM documentation.

    I've never been bothered by missing bridge devices whenever it happened in previous versions of openSUSE, partly because I hardly ever used default bridging devices(virtual networks) anyway. I've always used only bridging devices I created either because of necessity or preference. I subnet and supernet my networks carefully which requires design and that isn't supported by defaults. Also, I'm always suspicious of using defaults which can be a gross mistake... One primary example is the county library system where I live... It set up as one enormous Class A private network using the default subnet mask(Yes, it's a very big mistake obvious only to those who design networks. And, as usual once set up you can't really change it).

    As for your reference for forwarding to NAT networks
    https://wiki.libvirt.org/page/Networ...ng_Connections

    As usual, when you reference something that is very, very old only someone experienced can determine what is still relevant or not.
    So, a primary general recommendation is that if the material is new to you, DO SEARCH ONLY for recent documentation, the more recent the better.
    In general, the provided configuration should be able to forward to a NAT virtual network.
    But, as you probably suspect most people won't do that or prefer that method since the alternative which is to instead use a bridge device that is configured for bridging(ie shared) mode in the next section immediately below what you referenced is simple and straight-forward. But, don't follow what is described in the "Bridged networking (aka "shared physical device")" section which describes creating interface files manually... Just use YaST or use the "brctl addbr" command to create the device(default configuration) or use libvirt(configured correctly).

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  6. #16

    Default Re: Virtual Networking -some Basics - All OS

    @malcolmlewis:
    or any other moderator/administrator:

    With all respect, I think tsu2 is either NOT using openSUSE (instead using perhaps SLES) or his pride is slowly raising lately.
    He seems to only check the links he likes, thus ignored the openSUSE virtualization docs link I clearly mentioned in my last post, the one telling that a default virtual network was supposed to be created.
    It's clearly the openSUSE docs, so only way to install KVM in openSUSE is installing qemu and libvirt along! And if libvirt is also installed it should also have created the aforementioned default virtual network, which as I already said it doesn't!

    If it's a big bug I'm no longer eager to attempt to report it since last report about this has never been touched. Guess it's definitely better for a moderator/administrator to report bugs.

    Again, this is not being very helpful...

  7. #17
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    Default Re: Virtual Networking -some Basics - All OS

    On Fri 01 Sep 2017 03:36:01 PM CDT, F style wrote:

    @malcolmlewis:
    or any other moderator/administrator:

    With all respect, I think tsu2 is either NOT using openSUSE (instead
    using perhaps SLES) or his pride is slowly raising lately.
    He seems to only check the links he likes, thus ignored the openSUSE
    virtualization docs link I clearly mentioned in my last post, the one
    telling that a default virtual network was supposed to be created.
    It's clearly the openSUSE docs, so only way to install KVM in openSUSE
    is installing qemu and libvirt along! And if libvirt is also installed
    it should also have created the aforementioned default virtual network,
    which as I already said it doesn't!

    If it's a big bug I'm no longer eager to attempt to report it since
    'last report about this' (http://tinyurl.com/y9twdcc4) has never been
    touched. Guess it's definitely better for a moderator/administrator to
    report bugs.

    Again, this is not being very helpful...


    Hi
    Well I use SLES and SLED (and other SUSE products) as well as
    openSUSE The whole point of Leap is better synergy, both from end
    use, documentation, package maintenance.

    Again, with openSUSE documentation if something isn't right, then edit
    it accordingly if's it's wrong/not working etc so the next
    person to not hit the bumps you seem to have. The whole point of
    docs/wiki etc.

    I'm a command line junky, so old habits die hard and what I do/use
    works for setting up libvirt/kvm/qemu in either SLE or openSUSE.

    Why not give gnome-boxes a whirl as an interface to libvirt/qemu as
    this maybe what you need (and works with NetworkManager).

    --
    Cheers Malcolm °¿° SUSE Knowledge Partner (Linux Counter #276890)
    openSUSE Leap 42.2|GNOME 3.20.2|4.4.79-18.26-default
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  8. #18
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    Default Re: Virtual Networking -some Basics - All OS

    Quote Originally Posted by F_style View Post
    @malcolmlewis:
    or any other moderator/administrator:

    With all respect, I think tsu2 is either NOT using openSUSE (instead using perhaps SLES) or his pride is slowly raising lately.
    He seems to only check the links he likes, thus ignored the openSUSE virtualization docs link I clearly mentioned in my last post, the one telling that a default virtual network was supposed to be created.
    It's clearly the openSUSE docs, so only way to install KVM in openSUSE is installing qemu and libvirt along! And if libvirt is also installed it should also have created the aforementioned default virtual network, which as I already said it doesn't!

    If it's a big bug I'm no longer eager to attempt to report it since last report about this has never been touched. Guess it's definitely better for a moderator/administrator to report bugs.

    Again, this is not being very helpful...
    It's possible to install only KVM without libvirt on openSUSE, it's not advisable or default but possible.
    If you do that, then openSUSE/SUSE documentation does not apply.

    Your insistence not to use YaST to install KVM means that your situation is not guaranteed to be the same "default" everyone else begins with and highly inadvisable.
    Any comments related to your setup relates only to your own and no one else, and is OK as long as what you're doing is for educational purposes but is highly inadvisable for anyone/everyone who wants to start with a known stable setup from the beginning and just wants something that works, instead of exploring little seen corners.

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  9. #19

    Default Re: Virtual Networking -some Basics - All OS

    And your insistence of playing ignorant or blind starts to be a thing suitable for reporting to moderators.

    Quote Originally Posted by F_style View Post
    --Installed KVM yet again through Yast, but rejecting bridge offering.

    --Installed KVM with "zypper in -t pattern kvm_server" and enabled libvirtd service.

    Result of last 2 cases: no virtual networks at all created out of the box; I had to manually create one.
    What part of "last 2 cases" are you not able to get?
    The "2 cases" include the one installing *through Yast*. And even the zypper attempt using the exact command above installs recommended packages, which also includes libvirt itself. If what you said was true I'd have used the --no-recommends option in zypper (and I cannot remember if libvirt is even listed as a "recommended" package anyways!)

    What I'm seeing here now is, with permission of moderators to express, someone calling liar to someone else. I don't think this is appropriate...

  10. #20
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    Default Re: Virtual Networking -some Basics - All OS

    Seems to have developed into a confusion here, and not a very harmonious confusion either. I think perhaps we close the thread.
    Leap 42.3 & 15.1 &KDE
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