On 3/25/25 9:19 AM, gameplayer2019pl--- via Users wrote: I haven't tried it with IPv6 (and not even with IPv4 in a very long time), but as long as you don't have a <dhcp> section under your <ip>, libvirt shouldn't be starting its own dhcp server on the bridge (and since you have <dns enable='no'/> it shouldn't start up dnsmasq at all). I suppose it *might* have something to do with the firewall rules added for the particular type of network - since you have no <forward> element, that network will be an "isolated" network, and will have firewall rules added to prevent any traffic from traveling beyond that bridge device / subnet; this shouldn't affect communications between two guests connected to the same network though. If you want to test that theory, add <forward mode='open'/> to the network definition and restart it (then shutdown/restart both of your guests) - this will assure that no firewall rules will be added for the network. You may also want to doublecheck any firewall rules on the guest that's running the DHCP server. Oh, and also try offering IPv4 IPs and see if the other guest gets an IPv4 address but not IPv6.