The avahi-daemon fails to start with UEK R2 and messages such as the following are logged:

avahi-daemon[PID]: SO_REUSEPORT failed: Protocol not available
avahi-daemon[PID]: Failed to create server: No suitable network protocol available

The workaround for this issue is to comment out the disallow-other-stacks entry in the /etc/avahi/avahi-daemon.conf file as follows:

#disallow-other-stacks=yes

(Bug ID 19712845)