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Wiring and the network interface

REAC is raw Layer-2 Ethernet. There is no IP, no DHCP and no routing: the mixer and the stagebox talk directly over the wire with a dedicated EtherType. Everything below follows from that.

Use a dedicated wired interface

The interface the transport captures on must be:

  • Wired. Not Wi-Fi, not a USB tether, not a bridge to anything else.
  • Dedicated to REAC. Nothing else should share the segment. Management traffic, file copies and streaming on the same wire will not corrupt audio, but they will compete with it for the very steady packet cadence the link depends on.
  • Up, with no IP address. REAC needs no addressing. Give the interface no IPv4 and no IPv6; an address only adds unrelated traffic to a wire that should carry nothing else.

A second physical NIC (or a VLAN on a NIC whose other traffic you control) is the normal arrangement: one interface for management and the network, one for the stagebox.

Never use a mirrored switch port

This is the failure that is worth its own heading, because the symptom does not point at the cause.

A mirrored (SPAN / monitor) switch port delivers every frame twice — once as the real frame and once as the mirror copy — and it does so in both directions. Feed the transport from such a port and every block of audio is played twice. What you hear is granular, stuttery audio, on a link where the box establishes normally, phantom power works, and metering looks right. It sounds like a broken decoder. It is not.

Mirror ports exist for diagnosis. They are for watching a link, never for carrying one.

The transport does now drop byte-identical duplicate frames, and that guard is what makes such a link sound clean, so you may not notice you are on a mirrored port at all. Do not rely on it: it is a robustness guard against duplicated delivery, not a supported topology. On a correctly-cabled interface it does nothing.

If you suspect this, see granulated or stuttery box audio.

Cabling

  • Direct cable from the mixer's REAC NIC to the box is the simplest and the most reliable arrangement. Use it unless you have a reason not to.
  • Through a switch works. Give REAC its own switch, or its own VLAN on a switch you control, and make sure that the port the mixer uses is an ordinary access port — not a mirror destination, not a port with storm control or IGMP snooping doing anything clever to Layer-2 traffic it does not recognise.
  • Cat 5e or better, standard Ethernet lengths. REAC runs over ordinary Ethernet cabling.

The single-master rule

Exactly one device on a REAC segment may be the master. When openmixer drives a box, the mixer is the master: it owns the clock and drives the handshake.

That means:

  • Do not put a Roland desk that is also acting as master on the same segment. Two masters on one wire is not a configuration the box can resolve; the visible result is a box that never settles, or one that flaps between establishing and dropping.
  • Do not run two copies of the transport on the same interface.
  • If a real desk must own the segment, the transport can run as a slave instead, but that is a different rig topology and not what Setup configures for you.

Interface names

Interface names are configuration, never a compiled-in default. Find yours with:

ip -br link

Pick the wired interface that goes to the box and enter it in Setup → Adapters → REAC. If the machine has several similar-looking interfaces, unplug the stagebox and watch which one loses carrier.

Two names are configurable: the capture interface and the transmit interface. They are normally the same interface and Setup treats them as one; a split is only useful in diagnostic rigs.

A checklist before a show

ip -br link                       # the REAC NIC is UP, with no address
systemctl --user status reac-pw
journalctl --user -u reac-pw -n 50

Then look at the mixer's Patchbay: the box should be there, with the right number of inputs.