Q: QEMU/KVM (qemu:///system) VM has no network connection (could not obtain IP address via DHCP); works in user session Today I somehow cannot get my VMs on Virt/QEMU to connect to network. At last try I have Linux Mint client and it fails to connect via DHCP. Wired connection is present, I was able to disable and enable it with virsh domif-setlink LM_21 vnet0 up seeing result in client.
I've recently started to use the stack and network was working some days ago (ping worked from clients). BTW those clients were deleted, but I'm using out-of-the-box settings now and IIRC before, QENU/KVM connection DHCP 192.168.122.2 - 192.168.122.254, for VM NIC virtual network default: NAT, virtio. I've tried to read another related posts, but could not understand how to solve my problem. Any way to check DHCP working from Virt side? Any other things to see, try? TIA
# virsh net-list --all
 Name      State    Autostart   Persistent
--------------------------------------------
 default   active   yes         yes

Added 1:
I've tried dhclient wired_net_name on client from No ip address assigned to kvm guest after it's cloned from another guest. After that I saw additional entry in networks for manual connection, some 169... IP and default route 0.0.0.0. ping outside failed.
Added 2:
I think I now understand why networking worked before. It worked for user session. I've just created VM of same distro for user session connection and networking works in client. Network source: usermode networking in NIC of VM in virt-manager.
Does NAT in system session require some additional config work?
Added 3:
I've read https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/6/html/virtualization_host_configuration_and_guest_installation_guide/chap-virtualization_host_configuration_and_guest_installation_guide-network_configuration
I've checked
/etc/sysctl.conf and net.ipv4.ip_forward = 1 is commented. However I do not see how it may prevent obtaining IP address via DHCP by the client. And why Network source: usermode networking works w/out it?
