Vagrant hangs with message "Waiting for domain to get an IP address..."

The problem may be (it was in my case) that there are firewall rules preventing NAT firewall rules for the virbr0 network device created by Vagrant via libvirt, which may look like the following (excerpt of iptables -L -n):

Chain FORWARD (policy ACCEPT)
target     prot opt source               destination
ACCEPT     all  -- 0.0.0.0/0            192.168.121.0/24     ctstate RELATED,ESTABLISHED
ACCEPT     all  -- 192.168.121.0/24     0.0.0.0/0

One possible fix is to disable those restrictive rules (for example, clear all iptables rules before starting the Vagrant machine).