# Network troubleshooting

Network problems are the most common cause of a system that "won't connect" or a capture that stutters. Work through the checks below in order — most issues come down to **subnet**, **firewall/inspection**, or **bandwidth**.

## Components can't find each other

AR 51 is a **local-network** system: every component announces itself and is auto-discovered, but only within the **same subnet**.

- **Same subnet, same network.** The server, Mocap Studio, and every client must be on the same subnet. A client on `172.19.x.x` cannot reach a server on `192.168.x.x`.
- **No isolation between ports.** Guest networks, client isolation on a Wi-Fi AP, or per-port VLANs can block discovery. Put everything on one flat segment for first bring-up.

:::warning
If components are on different subnets they will **not** see each other, even though each one is "online". Fix the addressing before debugging anything else.
:::

## Mocap Studio finds OMS but not CVS

Mocap Studio shows the registration service (**OMS**) as connected, but the vision service (**CVS**) stays grey.

- **Update Mocap Studio** to a version **above 3.0.2.39** — this was a known networking fix.
- Confirm the server (CVS) is actually running and on the same subnet (see above).

## Skeletons don't appear in the Unity / Unreal client

The system runs and Mocap Studio shows data, but your engine client gets nothing.

- **Same network** — confirm the client machine is on the same subnet as the server.
- **Firewall / deep-packet inspection** — see below; this is the most common cause.
- **Try a different client class** — test PC vs. VR. We've seen a firewall doing deep-packet inspection break the PC app while a VR client worked.
- **Restart the client** application after the server is up.
- **On Wi-Fi**, a congested channel causes jerky motion and latency — prefer wired, or pick a clear channel.

## Disable deep-packet inspection

Security software (e.g. **Trend Micro**) that performs **deep-packet inspection** on all traffic can cripple throughput and block discovery.

- **Disable** the inspection feature, or add **exceptions** for the AR 51 server and clients.

:::warning
Unless removed or excepted, deep-packet inspection can cause serious performance and connectivity problems.
:::

## Cameras drop frames, flicker, or lose FPS

Camera issues are usually **bandwidth**, not the camera itself — the PC can't move every image into memory fast enough.

- **Don't use an ordinary router or consumer switch** for the cameras. Use a **direct connection** to the server's PCIe network cards, or the **qualified 100 G aggregation switch**. See [System architecture overview](/docs/network/architecture-overview).
- **Cables matter.** Use **Cat7** (or Cat6a for short runs). Keep unshielded Cat6a away from power cables to avoid interference.
- **Check the NIC slot.** A network card must sit in a slot that actually provides its rated PCIe lanes.
- A failing **Ethernet cable, SFP module, or PSU** will make one camera disconnect/reconnect — swap each in turn.

→ More camera-specific symptoms are in the [FAQ → Cameras](/docs/troubleshooting/faq#cameras).

## Using the 100 G switch

If you've chosen the aggregation-switch topology, the switch ports must be configured for **100 G / SFP28** before the server will see the uplink.

→ Follow [Configure the fs.com switch (100 G)](/docs/network/switch-100g).

## Still stuck?

- Re-check [System architecture overview](/docs/network/architecture-overview) for the supported topologies and cabling.
- Browse the [FAQ & common issues](/docs/troubleshooting/faq) for symptom-specific fixes.
- If the server won't start at all with a "no internet connection" error, it can't reach the licensing server — contact AR 51 support for an offline option.