Introduction
Most computers have multiple network adapters. This can present a problem with ipMIDI and Delta Control because multicast data (DAW control, Delta Control, MIDI Time Code, and MIDI Machine Control) will by default be forwarded to one adapter, defined automatically in the OS routing table. Without any intervention, the route chosen by the OS will be the adapter connected to the internet or your corporate network (the gateway adapter), not the connection to the console.
The simplest solution is to connect every device to an unmanaged switch (or your home router), and enable only one adapter on your computer, guaranteeing traffic has no choice but to be forwarded to the one connected adapter, and is therefore forwarded to all devices. Note an unmanaged switch is specified since IGMP Snooping on a managed switch may prevent multicast from being forwarded, as SSL consoles do not participate in IGMP.
If you must implement multiple network adapters, you will need to edit the routing table of your computer to ensure the multicast destined for ipMIDI and Delta Control are forwarded through the correct adapter (multicast destination addresses of 225.0.0.37 for ipMIDI and 225.0.0.38 for Delta Control).
To edit the routing table, apply the following commands either in the Terminal on macOS or Command Line on Windows:
macOS routing table
sudo networksetup -setadditionalroutes "macOS adapter name" 225.0.0.37 255.255.0.0 127.0.0.1
sudo networksetup -setadditionalroutes "macOS adapter name" 225.0.0.38 255.255.0.0 127.0.0.1
Replace "macOS adapter name" with the name of the Ethernet adapter on your Mac to which the SSL is connected, as shown in macOS System Network Preferences. If there is a space in the name you must contain in quotations.
Windows routing table
route add -p 225.0.0.37 mask 255.255.255.0 Windows adapter IP address
route add -p 225.0.0.38 mask 255.255.255.0 Windows adapter IP address
Replace Windows adapter IP address with the IP address of the Windows adapter connected to the SSL. Type ipconfig in cmd.exe to print adapter info to the prompt.
Caveats:
- Apple has periodically changed their method for persistent routing table changes. Should this happen in future, this process may need to be revisited. Google macOS persistent routing table.
- Reinstalling or updating the OS will remove static routes. The configuration process will need to be repeated.
- Anecdotally some consumer TP-Link brand switches do not pass multicast correctly.
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