Public IP on virtual machine network issue

Laine Stump
Mon, 14 Feb 2022 14:12:38 -0000

On 2/13/22 5:38 PM, Tom Ammon wrote:
> Can you post the output of iptables -L?
>
> By default, the bridge module in the kernel sends packets traversing the
> bridge to iptables (in the FORWARD chain I believe) for processing. So
> if you have configured a DENY policy on the FORWARD chain, or are
> otherwise filtering in the forward chain, you'll be affecting packets
> traversing the bridge. Check out this page for details on how to change
> this behavior:
> https://wiki.libvirt.org/page/Net.bridge.bridge-nf-call_and_sysctl.conf
>
<https://wiki.libvirt.org/page/Net.bridge.bridge-nf-call_and_sysctl.conf>

That information is *very* out of date; the situation has changed quite
a lot since that was written in 2014.

Filtering of packets traversing a bridge device are now only filtered if
the br_netfilter module is loaded, which isn't done by default. It *is*
autoloaded if certain types of iptables rules are added(I can't remember
the details of the type of rule though - there was a bug in iptables a
year or so ago where autoload of br_netfilter was triggered by libvirt
attempting to *remove* a rule of whatever type it was).

Anyway, unless "lsmod | grep br_netfilter" shows that you have
br_netfilter loaded, this entire path is a red herring (if you do have
it loaded, unload it, and try to figure out why it was loaded).

(Interestingly, this is the 2nd time this particular outdated page has
come up in the last week. Has something else broken somewhere that's
causing people to search out this page?)

>
> Tom
>
> On Sun, Feb 13, 2022 at 4:08 PM Marcin Groszek <marcin at voipplus.net
> <mailto:marcin at voipplus.net>> wrote:
>
>     I have been struggling with this for weeks and I was unable to find an
>     answer on line. Perhaps someone here can help me.
>
>     Oracle linux 8 running virtualization:
>
>     hardware node has a public IP address on interface bridge0 and physical
>     eno1 is a member of the bridge0
>
>     a virtual OS has interface bridged to lan and source is bridge0, Ip
>     address of virtual OS is also a public from same class as the
>     hardware node.
>
>     I can route in and out of virtual, I can ping from hardware node to
>     virtual and vice versa, so the routing works as it should, sort of.
>
>     When I try tracepath or traceroute from outside to virtual I get !H on
>     last hup
>
>     same result when I try to do the same form hardware node to virtual
>     I get !H
>
>     Also, when I telnet (TCP) to a specific port on virtual where I have a
>     daemon LISTENING OR NOT I get: No route to host. Same experiment works
>     just fine for ssh port.
>
>     Firewalld is not running, and I just have very basic iptables rules
>     like
>     allowing external address block to ssh to hardware node and to virtual
>     dropping connections from all other sources
>
>     This issue presented it self when I attempted to setup a galera node on
>     virtual and ports 4567 is responding but 4568 and 4444 are not, but the
>     daemons are running and I can clearly see lsoft showing
"LISTENING"
>
>     I capture the traffic and the tcp as well as udp are getting to the
>     virtual. Is there a preconfigured netfiltering that I am not aware of?
>
>     What am I missing?
>
>
>
>
>     --
>     Best Regards:
>     Marcin Groszek
>     Business Voip Resource.
>     http://www.voipplus.net <http://www.voipplus.net>
>
>
>
> --
>
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> Tom Ammon
> M: (737) 400-9042
> thomasammon at gmail.com <mailto:thomasammon at gmail.com>
>
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