Which frontend for KVM?!

Linux/FOSS Questions
81

No - VirtualBox creates the bridge internally… don’t ask me about the internals - it just works…

I just prefer the architecture of KVM… and not a big fan of Oracle in the first place (VirtualBox was originally a product from some German company that Sun Microsystems purchased)…

I guess as I have WiFi too - I have 3 NICs? I hardly EVER use the WiFi on my desktop machine… Having said that - I did have to use it last week - my shonky VDSL went down for 36 hours - so I had to use my phone as mobile hotspot and use my desktop’s WiFi to get online…

...
2: enx00e04c680151: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel master br0 state UP mode DEFAULT group default qlen 1000
    link/ether 00:e0:4c:68:01:51 brd ff:ff:ff:ff:ff:ff
3: enp39s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP mode DEFAULT group default qlen 1000
    link/ether 2c:f0:5d:74:48:b8 brd ff:ff:ff:ff:ff:ff
4: wlp41s0: <BROADCAST,MULTICAST> mtu 1500 qdisc noqueue state DOWN mode DEFAULT group default qlen 1000
    link/ether 68:54:5a:d3:53:74 brd ff:ff:ff:ff:ff:ff
5: br0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP mode DEFAULT group default qlen 1000
    link/ether 00:e0:4c:68:01:51 brd ff:ff:ff:ff:ff:ff
6: virbr0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state DOWN mode DEFAULT group default qlen 1000
    link/ether 52:54:00:16:f9:68 brd ff:ff:ff:ff:ff:ff
7: vnet0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master br0 state UNKNOWN mode DEFAULT group default qlen 1000
    link/ether fe:54:00:44:3e:81 brd ff:ff:ff:ff:ff:ff
16: vnet9: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master br0 state UNKNOWN mode DEFAULT group default qlen 1000
    link/ether fe:54:00:3c:ef:7f brd ff:ff:ff:ff:ff:ff

br0 and enx00e04c680151 have the same MAC address because that NIC is my USB 3 gigabit adaptor which is a slave to my bridge br0…
enp39s0 is my onboard gigabit NIC on my motherboard
wlp41s0 - my WiFi - not connected though
“vibr0” is what KVM / virt-manager uses if I run a VM in NAT or macVTAP…
And I’ve no idea what vnet0 and vnet9 are - possibly something to do with KVM using my bridge?
The MAC address of vnet9 is so close to the MAC address of my RHEL10 VM :
Host :

╭─x@titanii ~/MPZ/WEEDIAN  
╰─➤  ip link show vnet9
16: vnet9: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master br0 state UNKNOWN mode DEFAULT group default qlen 1000
    link/ether fe:54:00:3c:ef:7f brd ff:ff:ff:ff:ff:ff

Guest :

[x@fungzubz00 ~]$ ip link show enp1s0
2: enp1s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP mode DEFAULT group default qlen 1000
    link/ether 52:54:00:3c:ef:7f brd ff:ff:ff:ff:ff:ff
    altname enx5254003cef7f

And - I use to pull my hair out a few years back with those seemingly inane long NIC device names - it was frustrating… But I’ve since learned the value of them after a recent “pull my hair out” exercise where a vendor had disabled “predicable network interface names” and forced NIC devices to be eth0…eth7 (yeah 8 NICs) - but - two were gigabit copper, and 6 were 24 gigabit fibre - however EVERY single boot - the NIC device names were being randomly re-assigned (in Oraclie Linux 8)… Vendor’s solution (after we unpatched the copper ports)? Create a bond of ALL NIC devices! WTF? Yeah… Fortunately the bond ALWAYS picks a NIC that DOES NOT have “NO-CARRIER” or is NOT “state DOWN”…

82

You get a vnetx every time you start a VM with virt-manager.

“vibr0” is what KVM / virt-manager uses if I run a VM in NAT or macVTAP…
Right
If you use Open Network, it is virbr1
It would seem virbr1 has no iptables forwarding and that is why Open Network will not ping the internet link or anything beyond it.

The bottom line seems to be, Vbox has the facility to create and configure a bridge in the host, Vman does not… you have to setup a bridge by hand for Vman.

83

I tried the following

  • enable ip_forwarding in the host
  • add firewall-backend = "iptables" to `/etc/libvirt/network.conf.

It had no effect.
If I do iptables -L -v -n it lists a whole lot of forwarding rules for virbr0 ( the NAT link) but nothing for virbr1.

So I think you are right, one has to manually configure the forwarding in iptables if one uses Open Network.

Not sure I want that much pain.

84

Yes, virtual machines that are currently connected to bridge. vnet (virtual network interface)

They (vnet) show up on mine when using virt-manager. When i use qemu directly they will show up as tap