Description of problem: After installing a virtual Fedora 25 guest on a Fedora 26 host, networking is broken in the virtual guest because of conflicting interfaces ens3 and virbr0. Thus, ifconfig reports: $ ifconfig ens3: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500 inet 192.168.124.228 netmask 255.255.255.0 broadcast 192.168.124.255 inet6 fe80::9d60:424d:6e3f:1028 prefixlen 64 scopeid 0x20<link> ether 52:54:00:da:5a:22 txqueuelen 1000 (Ethernet) RX packets 9 bytes 1117 (1.0 KiB) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 38 bytes 5411 (5.2 KiB) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 72 lo: flags=73<UP,LOOPBACK,RUNNING> mtu 65536 inet 127.0.0.1 netmask 255.0.0.0 inet6 ::1 prefixlen 128 scopeid 0x10<host> loop txqueuelen 1 (Local Loopback) RX packets 96 bytes 6400 (6.2 KiB) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 96 bytes 6400 (6.2 KiB) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0 virbr0: flags=4099<UP,BROADCAST,MULTICAST> mtu 1500 inet 192.168.124.1 netmask 255.255.255.0 broadcast 192.168.124.255 ether 52:54:00:11:fe:b0 txqueuelen 1000 (Ethernet) RX packets 0 bytes 0 (0.0 B) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 0 bytes 0 (0.0 B) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0 When the host system is using Fedora 25, then the inet of interface ens3 is 192.168.122.x which does not conflict with the inet 192.168.124.x of interface vibr0. Version-Release number of selected component (if applicable): libvirt-3.1.0-1.fc26. How reproducible: Always (when certain conditions are met). Steps to Reproduce: 1. Install Fedora 25 in a virtual guest. 2. Reboot system. Actual results: The wired-connection icon exhibits a question mark, and name resolution is broken. Expected results: The wired-connection is working correctly including name resolution. Additional info: This issue is complex because is depends on the systes which are installed on the host and on the guest, respectively: 1. When the host system is using Fedora 25, too, no conflict occurs. 2. When the relevant virtualization-related packages are removed from the guest, then no conflict occurs, because interface virbr0 is absent right from the start. Therefore, no problem is ever observed e.g. after installing CentOS 7.x on the guest. Uninstalling libvirt packages is the safest manner to restore proper networking for the virtual guest. 3. When booting Fedora 25 live media (official or updated) on the guest system, no interface virbr0 is present at all, and thus no conflict occurs either. Interface virbr0 only appears after booting up the installed system, sometimes even only after additionally updating the kernel package.
*** This bug has been marked as a duplicate of bug 1146232 ***