Since the release of Junos v12.1x44D10 for branche SRX firewalls, Juniper added a feature called DNS-Proxy. This features enables the Junos device as a caching DNS server with several additional options. One of those feature is to define a Fully Qualified Domain Name (FQDN) with an IP address which overrides (if it exists) the entry in the 'official' DNS system on the Internet.