mDNS Repeater

Starting with VyOS 1.2 a mDNS repeater functionality is provided. Additional information can be obtained from https://en.wikipedia.org/wiki/Multicast_DNS.

Multicast DNS uses the reserved address 224.0.0.251, which is “administratively scoped” and does not leave the subnet. mDNS repeater retransmits mDNS packets from one interface to other interfaces. This enables support for devices using mDNS discovery (like network printers, Apple Airplay, Chromecast, various IP based home-automation devices etc) across multiple VLANs.

Since the mDNS protocol sends the AA records in the packet itself, the repeater does not need to forge the source address. Instead, the source address is of the interface that repeats the packet.

Note

You can not run this in a VRRP setup, if multiple mDNS repeaters are launched in a subnet you will experience the mDNS packet storm death!

Configuration

set service mdns repeater interface <interface>

To enable mDNS repeater you need to configure at least two interfaces so that all incoming mDNS packets from one interface configured here can be re-broadcasted to any other interface(s) configured under this section.

set service mdns repeater disable

mDNS repeater can be temporarily disabled without deleting the service using

set service mdns repeater ip-version <ipv4 | ipv6 | both>

mDNS repeater can be enabled either on IPv4 socket or on IPv6 socket or both to re-broadcast. By default, mDNS repeater will listen on both IPv4 and IPv6.

set service mdns repeater allow-service <service>

mDNS repeater can be configured to re-broadcast only specific services. By default, all services are re-broadcasted.

set service mdns repeater browse-domain <domain>

Allow listing additional custom domains to be browsed (in addition to the default local) so that they can be reflected.

set service mdns repeater cache-entries <entries>

Specify how many resource records are cached per interface. Bigger values allow mDNS work correctly in large LANs but also increase memory consumption.

Defaults to: 4096

Example

To listen on both eth0 and eth1 mDNS packets and also repeat packets received on eth0 to eth1 (and vice-versa) use the following commands:

set service mdns repeater interface 'eth0'
set service mdns repeater interface 'eth1'

To allow only specific services, for example _airplay._tcp or _ipp._tcp, (instead of all services) to be re-broadcasted, use the following command:

set service mdns repeater allow-service '_airplay._tcp'
set service mdns repeater allow-service '_ipp._tcp'

To allow listing additional custom domain, for example openthread.thread.home.arpa, so that it can reflected in addition to the default local, use the following command:

set service mdns repeater browse-domain 'openthread.thread.home.arpa'

Operation

restart mdns repeater

Restart mDNS repeater service.

show log mdns repeater

Show logs for mDNS repeater service.

monitor log mdns repeater

Follow the logs for mDNS repeater service.