libvirt / kvm bridged network question

[Sbob]

All;

I am moving from VMWare to KVM / libvirt / vitr machine manager

In VMWare I could tell a VM to use a bridged network and then the IP of 
that VM was accessible from other servers

I have seen setup guides on the web and they all seem to suggest that I 
need one additional IP interface on my KVM server for each bridged ip I 
want.

Is this true? Is there some way to easily replicate the way VMWare does 
it so I can just tell a VM to use an IP that is accessible from another 
server?

Thanks in advance

[Tom Horsley]

On Mon, 6 May 2024 16:28:18 -0600
Sbob wrote:
> Is this true? Is there some way to easily replicate the way VMWare does 
> it so I can just tell a VM to use an IP that is accessible from another 
> server?

I know nothing about VMWare, but I use a bridge for all of my
KVM virtual machines, and as far as the local network goes, they just
look like another physical machine on my local network. They can even
get assigned an IP addr by the DHCP server on my router.

[Samuel Sieb]

On 5/6/24 16:10, Tom Horsley wrote:
> On Mon, 6 May 2024 16:28:18 -0600
> Sbob wrote:
> > Is this true? Is there some way to easily replicate the way VMWare does
> > it so I can just tell a VM to use an IP that is accessible from another
> > server?
>
> I know nothing about VMWare, but I use a bridge for all of my
> KVM virtual machines, and as far as the local network goes, they just
> look like another physical machine on my local network. They can even
> get assigned an IP addr by the DHCP server on my router.

I'm curious what the configuration for that looks like.  Does the host 
use the bridge interface as well?

[Tom Horsley]

On Mon, 6 May 2024 16:15:00 -0700
Samuel Sieb wrote:
> I'm curious what the configuration for that looks like.  Does the host 
> use the bridge interface as well?

Yep. I make the physical ethernet port on the host be a part of the
bridge (and force the bridge to use the same MAC address as the
physical port), so there is always one member of the bridge. Then
the virtual ethernet ports in the virtual machines are made part of
the same bridge.

Here's my notes on how I first set things up with network manager
(when I finally broke down and started using network manager :-).

nmcli con show
nmcli con add ifname br0 type bridge con-name br0
nmcli con add type bridge-slave ifname eth0 master br0
nmcli con down "Wired connection 1"
nmcli con up br0
nmcli con show
nmcli con mod br0 ipv4.ignore-auto-dns yes
nmcli con mod br0 bridge.mac-address nnn...
nmcli con modify br0 bridge.stp no

That last step of turning off stp is important to make the network
start rapidly. Depending on how someone else would use it the
ignore auto dns may not be appropriate.

[Samuel Sieb]

On 5/6/24 15:28, Sbob wrote:
> In VMWare I could tell a VM to use a bridged network and then the IP of 
> that VM was accessible from other servers
>
> I have seen setup guides on the web and they all seem to suggest that I 
> need one additional IP interface on my KVM server for each bridged ip I 
> want.
>
> Is this true? Is there some way to easily replicate the way VMWare does 
> it so I can just tell a VM to use an IP that is accessible from another 
> server?

Use the macvtap option with your ethernet interface name.

[Jeffrey Walton]

On Mon, May 6, 2024 at 6:28 PM Sbob  wrote:
> All;
>
> I am moving from VMWare to KVM / libvirt / vitr machine manager
>
> In VMWare I could tell a VM to use a bridged network and then the IP of
> that VM was accessible from other servers
>
> I have seen setup guides on the web and they all seem to suggest that I
> need one additional IP interface on my KVM server for each bridged ip I
> want.
>
> Is this true? Is there some way to easily replicate the way VMWare does
> it so I can just tell a VM to use an IP that is accessible from another
> server?

I don't think there's an easy way when compared to VMware and VirtualBox
since both of them provide the support out-of-the box.

For some instructions from the libvirt folks, see <
https://lists.libvirt.org/archives/list/[e-mail]/thread/V27YY....
(The docs should really cover the use case).

Jeff