Multicast DNS

Multicast DNS provides hostname resolution as well as advertises services to local computers. It is only available on a LAN, and will not work over VPN.

OS X

OS X relies heavily on multicast DNS for name resolution, and will often prefer mDNS over a local DNS server for primary lookups.

Using host will use the DNS server to do a lookup.

Using ping will use mDNS to do the lookup.