Run the following commands to disable the mDNS service on CentOS 6 and lower:
service avahi-daemon stop chkconfig avahi-daemon off
Or when you have CentOS 7:
systemctl stop avahi-daemon systemctl disable avahi-daemon
What is the avahi-daemon service?
The Avahi mDNS/DNS-SD daemon implements Apple’s Zeroconf architecture (also known as “Rendezvous” or “Bonjour”). The daemon registers local IP addresses and static services using mDNS/DNS-SD and provides two IPC APIs for local programs to make use of the mDNS record cache the avahi-daemon maintains. First there is the so called “simple protocol” which is used exclusively by avahi-dnsconfd (a daemon which configures unicast DNS servers using server info published via mDNS) and nss-mdns (a libc NSS plugin, providing name resolution via mDNS). Finally there is the D-Bus interface which provides a rich object oriented interface to D-Bus enabled applications.