I accidentally entered a command line as follows:
/usr/bin/qemu-kvm -drive
file=/scratch/images/beth/windows/win2k3_32_R2.dat.10G.img,if=ide -m
2048 -boot cd -net nic,model=rtl8139 -net tap,script=/etc/qemu-ifup -vnc
:12 -usbdevice tablet -monitor stdio -net nic,model=e1000 -net
tap,script=/etc/qemu-ifup
and the machine's networking broke, requiring a network restart to get
it back in order. The second -net tap,script=/etc/qemu-ifup causes the
problem.
/var/log/messages shows
tap0: received packet with own address as source address
I don't have time at the moment to look into what's going wrong. Just
wanted to make people aware.
Beth Kon