Why Does P2-622 to P2-RS Wireless Ethernet Drop Out?

The P2-622 and P2-RS communicate correctly through a direct Cat6 cable, but the wireless point-to-point link intermittently loses the remote unit. Treat that result as a network-path fault: packet loss, unstable radio association, excessive delay variation, or a bridge that does not pass the required Ethernet traffic transparently.

Reject the usual quick fixes

Do not start by changing controller logic, replacing the remote unit, or extending communication timeouts. The successful direct connection shows that the controller, remote I/O configuration, addressing, and application logic can operate together. A longer timeout might hide an occasional late packet, but it will not repair a radio link that repeatedly drops frames or renegotiates.

Changing both radios to arbitrary frequency or channel settings also fails when interference, alignment, or bridge mode is the actual problem. Both ends must use compatible radio settings, but matching settings alone do not prove link quality.

Likewise, seeing each device respond occasionally does not prove that the bridge can carry sustained control traffic. Engineering access may survive losses that cause cyclic remote-I/O communication to fail.

Check before continuing: reconnect the direct cable and confirm that the P2-RS remains present without loss. If it also drops on copper, stop troubleshooting the radios and correct the controller, remote unit, cable, power, or Ethernet configuration first.

Lock down the wired baseline

Record the working arrangement before inserting the wireless equipment. Capture the P2-622 address, the P2-RS address, subnet settings, switch arrangement if present, and the controller indication used to detect loss of the remote unit. Do not change these values while testing the bridge.

1. Connect the P2-622 directly to the P2-RS with the known-good Cat6 cable.
2. Run the machine through the operating states that produce normal I/O traffic.
3. Observe the remote-unit status for long enough to cover the operating cycle.
4. Record any controller diagnostic, timestamp, or loss indication that appears.
5. Move only the Ethernet path to the radios; leave the application configuration unchanged.

This isolates one variable. If the fault returns immediately after the bridge is inserted, investigate the bridge and radio path rather than rewriting the control program.

Check before continuing: confirm a stable wired run and a repeatable failure only when the wireless path replaces the cable.

Configure one transparent Ethernet bridge

Use the point-to-point pair as a transparent Layer 2 bridge. The radios should forward Ethernet frames between the two wired ports without creating a second routed network, translating addresses, providing mesh service, or placing either endpoint behind a client-isolation feature.

Do not confuse each radio's management address with the addresses of the automation devices. Management addressing lets maintenance configure the radios; transparent forwarding carries the controller traffic through them.

If the current UeeVii pair cannot operate as a transparent bridge or its interface offers no useful link diagnostics, replacement becomes a practical decision. Select a point-to-point product that explicitly supports transparent Ethernet bridging and exposes signal, association, error, and traffic statistics.

Check before continuing: verify that both automation endpoints remain in their known working address arrangement and can communicate through the bridge without routing or mesh features.

Stabilize the radio path

A radio pair can show “connected” while losing enough frames to interrupt remote I/O. Control traffic exposes brief fades, interference, and reassociation events that ordinary configuration access may not reveal.

1. Establish clear line of sight between the antennas. Rock faces, equipment, stockpiles, and moving machinery can obstruct or reflect the path.
2. Mount both ends rigidly. Vibration or wind movement can shift a directional antenna away from its best alignment.
3. Align the radios using their built-in signal indication rather than visual aim alone.
4. Confirm that both ends use the intended frequency and channel.
5. Inspect radio diagnostics for association resets, packet errors, retransmissions, or changing signal quality while the process operates.
6. Check power and Ethernet connections at both radios. A power interruption or marginal connector looks like a wireless dropout from the controller.

Bench success does not validate the production path. Short distance and unobstructed alignment can mask interference, reflections, antenna movement, and environmental exposure.

Check before continuing: watch the radio diagnostics while operating nearby equipment and confirm that the association remains continuous with no coincident error increase.

Test the traffic that actually fails

Test the P2-RS as remote I/O, not merely as a reachable Ethernet address. A management page or occasional diagnostic response proves only that some frames cross the link. Cyclic exchanges are sensitive to consecutive lost or delayed packets.

1. Start with the machine in a safe, nonproductive state.
2. Run the controller with the wireless bridge installed.
3. Monitor the controller indication that reports loss of the P2-RS.
4. At the same time, monitor each radio's link and Ethernet statistics.
5. Record whether the controller loss aligns with a radio reassociation, Ethernet-port interruption, packet-error increase, or power event.
6. Repeat the test during normal plant activity, including equipment movement that may affect line of sight.

If the controller reports a loss but the radio association remains stable, inspect bridge filtering, Ethernet-port negotiation, cabling, and power. If association resets at the same moment, correct alignment, interference, mounting, or radio selection.

Check before continuing: produce a test where the controller remains connected and radio statistics remain stable through the same conditions that previously caused the failure.

Harden the installation and verify end to end

Get production running with a stable bridge, then make the installation maintainable. Secure antenna mounts, protect Ethernet terminations, document radio roles and settings, and preserve the known-good configuration. Keep controller and remote-I/O addressing identical to the wired baseline.

For final verification, cycle power using the site's approved startup sequence and confirm that the bridge reassociates and the P2-RS returns without manual intervention. Exercise all required inputs and outputs, then observe the link across a representative operating period. Review controller diagnostics and radio counters after the run; a connected status with accumulating errors is not a pass.

If selecting replacement radios, prioritize transparent Layer 2 operation, usable link diagnostics, installation suitability, and adequate range and directionality for the actual path. Product families such as Ubiquiti AirMax, including NanoStation 5AC Loco or the more directional LiteBeam 5AC, were identified as possible alternatives, but verify their current specifications and environmental suitability before purchase.

Final check: confirm automatic recovery after startup, continuous P2-RS presence, correct field I/O operation, and stable radio statistics under production conditions.

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