There doesn’t seem to be a way to specify the network adapter for the NDI operators. This is a pretty big deal for those with multiple nics trying to do NDI studio work. In fact I would have thought it’d make sense to allow any network operators (Touch In/Out etc) to pick which network they’re using.
Is this something that you’ve seen in other NDI software? As far as I know this isn’t something NDI allows for.
For NDI, you don’t really have to worry about multiple NIC for IN and OUT, NDI since version 3.0 or above has support multiple NIC and can automatically load balance multiple stream over Multiple NIC even without Link Aggregation, so if you have multiply NIC and you are running into bandwidth issue, just plugin more NIC into the switch, it will figure the load balancing by itself. (See Technology Section in NDI Wiki Page).
However if you are worry about the NDI network crossing over to other network that are sensitive to multicast traffic. Then I will suggest the following one of the two solutions:
Option 1) Using Firewall to block NDI program. If you only have windows firewall (which is quite limited), in network location for windows, set all NIC that you plan to use for NDI and set them as home or office (private network), and set all of your non-NDI traffic that you are worry about multicast traffic and put them onto (Guest / Public) network location. Then under windows firewall setting, block all NDI related program on the Public network location (https://www.technipages.com/blockunblock-programs-in-windows-firewall). Note: This will only be good if you have a clear definition of program that are using NDI network and other program that don’t use the NDI network. If you have program that needed to cross over to both, then you need to do it another way. (or get a proper firewall program, as windows firewall program is quite limiting).
Option 2) If you are using program that need to cross over both network, option 1 will not work. So you will need to block all the Port that are used by NDI. You can either do this on the switch level (which you will need to consult your switch user menu), or you can also do it via the windows firewall rules.
(see how to do it here: https://www.hostwinds.com/guide/how-to-open-or-block-ports-using-windows-firewall/)
Essentially, you will want to block the following ports that are used by NDI:
Port: 5353 (For NDI mDNS Self Discovery / Bonjour)
Port: 5960 (NDI Messaging Server to allow direct NDI connection)
Port: 5961 onward (depending on the number of NDI stream on your network, blocking Port 5961 onward will stop your stream from being discover, as Port 5961 is used for the first stream, second stream will be 5962, etc etc).
Port: 49152 to 65535 (These are the Ephemeral Ports that are used by NDI for communication, if you want to check the exact Ephemeral Ports on your computer, use the following command on windows: netsh command, blocking them will prohibit any NDI comms on your network).
That should be enough to prohibit NDI from working on your second NIC.
Hope this helps.