Multicast DNS and Service Discovery
Two extensions to the DNS protocol are multicast DNS (mDNS) and DNS Service
Discovery (DNS-SD). mDNS extends the Domain Name Service system to operate over link-local
multicast. DNS-SD adds support needed to discover network services over DNS.
Multicast DNS (mDNS) provides a naming service system that is easy to set
up and maintain, for computers on a local link. All participating network devices
on the same local link perform standard DNS functions, using multicast DNS rather
than unicast, and do not need a unicast DNS server.
For administrators, the primary advantage of mDNS is that no unicast DNS server
needs to be maintained on the local network. There is no need, for
example, to update and maintain host names in files to resolve hostname to
IP address for devices on the local link that are using mDNS.
Network services include printing, file transfer, music sharing, servers for photo, document and
other file sharing, and services provided by other local devices. DNS service discovery
support in the Solaris OS includes open source framework and tools from Apple
to enable applications to advertise and discover network services, using DNS on the Solaris
For users, network service discovery makes computing easier by enabling users to browse
for services on the network, rather than needing to find the service manually.
Existing standards, and work done by other companies and groups, assure that cross-platform
support is available.
Use the Service Management Facility (SMF) to administer the mDNS daemon. You
can use SMF to start and stop the mDNS service.
For an overview of SMF, refer to Chapter 16, Managing Services (Overview), in System Administration Guide: Basic Administration. Also refer to the
svcadm(1M) and svcs(1) man pages for more details.
For mDNS to function, it must be deployed on all peers that are
to participate in mDNS. It is used to advertise the availability of services
provided on the peer.
Multicast DNS and Service Discovery are both installed by default in the “all”
cluster, when installing the Solaris OS. For other types of devices, for example,
printers, music, video, and communication devices, many already have mDNS installed.
In addition to being installed, mDNS must be enabled, and must be
included in the /etc/nsswitch.conf file. See nsswitch.conf(4)
For the Solaris OS, as root, or as a user with appropriate
privileges, enable mDNS on each computer that will participate in mDNS.
# svcadm enable svc:/network/dns/multicast:default
Enabling mDNS this way persists through upgrades and reboots. For more information, see
To be able to resolve local hosts, edit the nsswitch.conf file and add
mdns to the list of name services. For example, the file might
look like the following:
hosts: files dns mdns
ipnodes: files dns mdns
For an example of the form such a file should take, see
Review Errors or Messages
Check the multicast DNS service log for errors or messages.
mDNS and dns-sd Tool
Use the dns-sd command as a network diagnosis tool, to browse and
discover services, similar to how you would use ping (1M) or traceroute (1M).
The dns-sd command is intended primarily for interactive use, mainly because its command
line arguments and its output format can change over time, which makes invoking
it from a shell script unpredictable and risky. Additionally, the asynchronous nature of
DNS Service Discovery does not easily lend itself to script-oriented programming.
For complete dns-sd information, see the man page for dns-sd (1M) and to
incorporate DNS service in applications, see the libdns_sd (3DNS_SD) man page.
EXAMPLES of the dns-sd command
Advertising a printing service
The following command advertises the existence of LPR printing service on port 515
on “My Test” machine, so that it will be available to DNS-SD compatible
dns-sd -R "My Test" _printer._tcp. . 515 pdl=application/postscript
For this registration to be useful, the LPR service should be available on
Advertising a web page
The following command advertises a web page being served by an HTTP
server on port 80 on "My Test" machine. The web page will
appear on the Bonjour list in Safari and other DNS-SD compatible Web clients:
dns-sd -R "My Test" _http._tcp . 80 path=/path-to-page.html