I run Ubuntu 21.04 server (GNU/Linux 5.11.0-1016-raspi aarch64) on a Pi 4 which is connected to my LAN through its ethernet port. I have a MOTU UltraLite-mk5 soundcard attached directly by USB. I would like to be able to access the UL5 over the network from my Mac for control purposes. Is there a way I can configure the Pi 4 to allow the UL5 to acquire its own IP address which can be reached from the LAN?
By way of background, if the UL5 is directly connected by USB to my Mac, I can direct sound to the UL5 and simultaneously access the UL5 using control software provided my MOTU (CueMix5). When directly connected, the UL5 is listed in the Mac's System Preferences | Network tab as connected with its internal 169.254.1.243 address. I've also noted that the CM5 app can connect to a UL5 over the network if given the UL5's IP address, but I've not tested that since I don't know how to connect the UL5 directly to the network by USB ... hence the question!
So I'm guessing the steps (none of which I fully understand!) will involve:
(1) getting a second LAN IP address on the RPi4's NIC (so the CM5 software can address that IP address from another networked machine). I know an NIC can have more than one IP address. I'd like to set up a second address, ideally acquired from the network's DHCP server, but the key thing is that the IP address needs to work with the rest of the setup, in particular, step (3). For that reason, does this second LAN IP address need to be static? And what CLI instruction do I need to set it up?
(2) configuring a USB network connection to the UL5 so both RPi4 and UL5 can talk to each other. I can see that the MOTU software installation on my Mac for the UL5 creates a USB network service (called UltraLite-mk5) and if I knew the relevant CLI instructions for Mac I could examine what has been set up so I could reproduce it on the RPi4. But I don't know yet how to do this. Can you help me with this?
(3) mapping that second IP address set up in (1) to the RPi4's USB connection to the UL5, so that network traffic addressed to the UL5's network IP is forwarded directly by the RPi4 via the USB network service to the UL5, and vice versa. Sounds simple enough! And if you know what the CLI instructions are, I guess it is. Help!
No doubt you can tell from my description that I don't have a deep understanding of networking, and I've only recently started to get to grips with the CLI of Ubuntu, so please pitch your replies at that level. Many thanks for reading.
