Setting up a network between the two PCs
When a DMA build needs a network link at all, and how to set one up with a direct cable, router or switch. It covers static or DHCP addressing, subnets without jargon, firewall rules and a ping test.
Short answer
Most DMA builds need no network link; only KMBox Net, a browser-based radar, or remote flashing and remote desktop require one. For those, one Ethernet cable with static addresses in one subnet is the simplest reliable path; test it with ping before blaming software.
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Do you need a network link at all?
A plain DMA build needs no network link between the two machines, because the card talks over PCIe and USB and neither of those uses IP. You need a network only when something specifically asks for one, and four things do. The first is a network-attached input device such as a KMBox Net variant, and the second is a radar that you view in a browser on another device. The other two are remote desktop into a headless second PC and pushing a firmware file across without a USB stick. If none of those is in your plan, skip the network setup and spend the time on the USB path instead.
Which way should you connect the two machines?
All three work, but they differ in what you have to configure by hand and in what else can reach the machines.
| Topology | What it is | Addressing | Good for | Watch out for |
|---|---|---|---|---|
| Direct cable | One Ethernet cable between the two machines' network ports | Static on both ends. No DHCP server exists on a two-node link | The simplest reliable link, and the only one with no third device to fail | Uses the only Ethernet port on each machine; neither gets internet through it |
| Existing router | Both machines on the LAN you already have, by cable or Wi-Fi | DHCP works out of the box; reserve the addresses or set them static | Machines that also need internet, and a phone or tablet joining as a radar screen | Client isolation on some routers blocks device-to-device traffic; Wi-Fi adds latency and jitter |
| Unmanaged switch | A small switch both machines plug into, with or without an uplink to the router | Static if there is no uplink, DHCP if the router is upstream | More than two devices, or keeping the DMA traffic on its own segment | One more power supply and cable to fail; a switch does not hand out addresses by itself |
A wired link is better than Wi-Fi for anything that carries input or per-frame data, so use Wi-Fi only for a phone acting as a passive radar screen.
What is a subnet?
An IP address has two parts: one says which network you are on, and the other says which machine it is on that network. The subnet mask says where the split falls, so with the usual mask 255.255.255.0 the first three numbers are the network and the last is the machine. That makes 192.168.50.10 and 192.168.50.11 two machines on one network that can talk directly. By contrast, 192.168.50.10 and 192.168.1.11 are on two different networks and cannot talk without a router between them. Getting this wrong is the most common reason two machines on the same cable cannot see each other.
Addresses to use for a direct cable link
If you have no reason to prefer other numbers, copy this plan. Both machines get an address on the same network and the same mask but no gateway, because on a two-node link there is nowhere to route to.
- Second PC address
- 192.168.50.10
- Game PC or device address
- 192.168.50.11
- Subnet mask
- 255.255.255.0
- Default gateway
- Leave empty on a direct cable link
- DNS
- Leave empty. Use IP addresses in the software configuration
- Network profile
- Private, not Public. Windows firewall blocks far more on a Public profile
How to set a static IP address in Windows
Do this on both machines, changing only the last number of the address each time.
- Connect the cable and confirm that the link lights are on at both ends
- Open Settings, then Network and internet, then Ethernet
- Set the network profile for that adapter to Private
- Find IP assignment and choose Edit, then Manual, then turn IPv4 on
- Enter the address and subnet mask from the addressing plan, and leave the gateway and DNS empty
- Save, then repeat on the other machine with the other address
- Before you open any software, run the ping test that follows
How to test the connection with ping
Run these commands in a command prompt, in order: first confirm that your own address is the one you set, then confirm that the other machine answers. If ping fails, no amount of configuration inside the application will help.
ipconfig /all
ping 192.168.50.11
ping -t 192.168.50.11
arp -a
netsh advfirewall firewall add rule name="ICMPv4 Allow Ping Requests" protocol=icmpv4:8,any dir=in action=allowWarning
Which firewall rules to add
On a Public profile, Windows firewall blocks most inbound traffic, including ping, and setting the adapter to Private fixes most of that. Some applications, such as a web radar server or a remote-flashing tool, still need an inbound port. Allow that one application or that one port on the Private profile only, and leave the Public profile alone. Turning the firewall off entirely is not the fix, and it is a bad habit on any machine that ever touches another network.
Common network problems and their fixes
Each row describes a pattern from real support tickets. Start with the first row and work down the list in order.
| Symptom | Likely cause | Fix |
|---|---|---|
| Ping times out in both directions | Adapter profiled as Public, so Windows firewall drops inbound ICMP | Set both adapters to Private or add the inbound ICMPv4 echo rule from the ping test, then ping again |
| ipconfig shows an address starting 169.254 | The adapter asked for DHCP, found no server, and self-assigned | Set static addresses on both machines, or put a router or DHCP-capable device in the path |
| Ping by IP works, ping by machine name fails | There is no name resolution on a direct link | Use IP addresses everywhere in the software configuration, because name resolution is not needed for this |
| Ping succeeds but the application cannot connect | The path is fine; the port is wrong or blocked | Confirm the port in the application's settings, then allow that port inbound on the listening machine's Private profile |
| Worked yesterday, nothing today, nothing changed | DHCP handed out a different address after a reboot | Move to static addressing, or reserve the address on the router so it never changes |
| Two devices on the same Wi-Fi cannot reach each other | Client or AP isolation is enabled on the router | This is a router setting, not a Windows one, so turn client isolation off for that network or use a cable |
Network questions
Do I need a crossover cable for a direct link?
No, any modern Ethernet port auto-negotiates the pairs, so a standard patch cable works between two machines.
Will the second PC lose internet if I use its only Ethernet port for the direct link?
Yes, that port will carry only the direct link. For internet, use Wi-Fi or add a USB Ethernet adapter on a port that the card is not using.
Is it safe to put both machines on my home LAN?
It is normal and it works, but anything else on that LAN can reach both machines. Keep the firewall on and keep your rules scoped to the Private profile.
Should the game PC be on this network too?
Only if something specifically needs it, such as remote desktop into the game PC or a network input device wired that way. The DMA read path itself does not use the network at all.
Can I use Wi-Fi for a KMBox Net device?
It often works technically, but in practice you should use a cable. Input timing is the one part of this stack that is sensitive to jitter, and Wi-Fi adds jitter.
Sources
Standard home networking applied to this build, with the symptoms that keep coming up in the team's support tickets.
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