If you boot multiple qemu images on the same machine, the first works fine, the guest gets the address 192.168.7.2 and the host 192.168.7.1. The second guest should get 192.168.7.4 and host 192.168.7.3. The guest network interface never comes up though and this leads to all kinds of interesting failures. Its likely part of the reason for some of the failures seen on the autobuilder but I reproduced this locally.
This was fixed with a combination of http://git.yoctoproject.org/cgit/cgit.cgi/poky-contrib/commit/?h=nitin/x32&id=faac9eda28d519598b4b566a3150645e4594d5d4 and http://git.yoctoproject.org/cgit/cgit.cgi/poky-contrib/commit/?h=nitin/x32&id=bbc8afb2e20fad083c40c614a79e68b7fdfc5f89