I'm running current Rawhide, a pretty clean install - clean installed F15 and updated to Rawhide shortly after - on my desktop. I tried to set up a VM, following the 'normal' process: 'yum groupinstall Virtualization', then use virt-manager's wizard to set up a VM. Normally, networking would work in the guest using the default NAT setup; this is how it's always been for me before, with F15 and F14. But now it doesn't work, the guest gets no working network connection. There is an eth0 interface, but it always fails to get an IPv4 address via DHCP.

I did not do anything unusual to the configuration of virt-manager or libvirt or qemu or anything. I did some troubleshooting via IRC with acathrow, who said he couldn't see anything out of place about the setup. We tested:

* Disabling firewall
* Enabling IPv4 forwarding, which seems to be disabled by default (echo 1 > /proc/sys/net/ipv4/ip_forward )
* Removing virbr0-nic from the bridge
* Loading vhost-net module

none of that seemed to make any difference. Right now I have the vm set up to use virtio for the network interface, but at first I was testing with 'Hypervisor default' - I'm guessing that's rtl8139? - and it didn't work either. I've tried both Windows (XP) and Fedora (current Rawhide XFCE live image) in the guest, so I don't think the guest is to blame.

I can provide remote access to the system if it will help anyone to diagnose the problem.