Communication returns after the switch port and relay Ethernet interface use compatible speed and duplex settings. Start at the physical link, identify the installed T60 interface, then follow the packet from the client through the switch to the relay. A switch forced to half duplex while the relay is forced to full duplex creates a duplex mismatch; changing speed alone will not correct it.
Where does the Ethernet path stop?
The request starts at the engineering workstation, control system, or other Ethernet client. It crosses the client network interface and switch, exits the switch port connected to the T60, and reaches the relay Ethernet interface. Check each hop in that order, but diagnose the relay-facing physical link first because its known settings conflict.
| Path element | Reading to take | Meaning | Next check |
|---|---|---|---|
| Relay-facing switch port | Link state, negotiated or configured speed, duplex, and error counters | No link indicates a media, interface, or speed compatibility problem. Rising errors indicate a physical-layer or duplex problem. | Identify the installed relay interface. |
| T60 Ethernet interface | Media type, supported speed, duplex configuration, and link indication | The installed option defines whether copper or fiber is present and whether 10 or 100 Mbps operation is possible. | Match switch settings to the interface. |
| Client-to-relay network path | Client address, relay IP address, subnet path, and reachability | A healthy link with no IP reachability moves the fault above the physical layer. | Check addressing and packet delivery. |
| Application session | Destination address, configured service, connection result, and timeout behavior | Successful IP reachability with a failed application session points to service configuration or filtering. | Inspect the application configuration. |
Which Ethernet interface is installed in the T60?
The T60 CPU includes an RS-232 port and may be equipped with RS-485, 10/100 Base-F, or 10/100 Base-T interfaces in particular combinations. Do not select a switch speed until the installed option is identified. Read the option code from the relay and compare it with the relay manual, or inspect the rear interface and its media connection.
| Observed interface | What it establishes | Required decision |
|---|---|---|
| Copper Ethernet connector | The interface is a twisted-pair Ethernet option rather than fiber or serial. | Determine whether the installed option supports both 10 Mbps and 100 Mbps. |
| Fiber Ethernet connection | The switch port, fiber type, and relay optical interface must be compatible. | Check the option documentation before choosing speed or duplex. |
| Serial connector only | The inspected connector is not the Ethernet data path. | Locate the actual Ethernet option or use the applicable serial configuration. |
A previously encountered fiber configuration used 820 nm multimode fiber and half duplex, but that observation does not identify every T60 option. The option code and rear hardware decide which settings apply to this relay.
Does the link have a duplex mismatch?
The reported switch setting is half duplex while the relay is set to full duplex. That is a mismatch. In half duplex, the interface expects shared-medium access behavior and treats overlapping transmission as a collision. In full duplex, the interface transmits and receives independently and does not use collision handling. When only one side operates in half duplex, traffic may pass intermittently while frames are lost or retried under load.
| Switch setting | Relay setting | Expected result |
|---|---|---|
| Half duplex | Full duplex | Invalid pairing; correct duplex before investigating application timeouts. |
| Half duplex | Half duplex | Duplex is aligned; continue with speed, media, and error checks. |
| Full duplex | Full duplex | Duplex is aligned if the installed relay interface supports this mode. |
| Automatic negotiation | Compatible automatic behavior | The interfaces can select a common mode when both sides support and use compatible negotiation. |
Read the switch counters before and after changing the setting. CRC or frame errors point toward media or physical signaling. Collision-related counters on the half-duplex side, combined with poor application performance, support the duplex-mismatch branch. Clear or record the counters so old faults are not mistaken for new ones.
Should the switch use 100 or 10 Mbps?
If the installed port is capable of 100 Mbps, it can detect the packet speed and respond at the compatible rate. Use 100 Mbps only after confirming that capability from the option code or manual. If the installed Ethernet option does not support 100 Mbps, configure the switch for 10 Mbps.
| Hardware finding | Switch speed decision | Verification reading |
|---|---|---|
Option documentation lists 10/100 operation |
Use a compatible automatic setting, or force the same supported speed on both ends if required by the installation. | Stable link indication and matching operational speed. |
Interface supports only 10 Mbps
|
Set the switch port to 10 Mbps. |
Link comes up at 10 Mbps without accumulating errors. |
| Capability remains unidentified | Do not guess between 10 Mbps and 100 Mbps. |
Read the relay option code, rear labeling, and applicable manual table. |
Speed and duplex are separate decisions. A common speed does not repair a half/full duplex mismatch, and matched duplex cannot make unsupported media or speed combinations link.
Can packets reach the relay after layer one is corrected?
Once link state, media, speed, and duplex are correct, follow the packet above the physical layer. TCP/IP communication requires an IP address in the relay. Compare the relay address with the address used by the client and determine whether the destination is local or must cross a routed hop.
- Confirm that the switch reports the relay port up at the intended speed and duplex.
- Record interface counters, send test traffic, and check whether error, discard, or collision counters increase.
- Read the relay IP address from its configuration and compare it with the client destination.
- Check the client address and subnet configuration. If the relay is outside the client subnet, verify the configured route and each intervening hop.
- Test basic IP reachability using an approved diagnostic method for the network. If reachability fails, inspect address duplication, switching path, VLAN membership, and routing before testing the application.
- If IP reachability succeeds, verify that the application targets the relay's configured address and required service. Read the service or port setting from the relay and client configuration rather than assigning an undocumented value.
A failed link keeps every higher-layer test from being meaningful. A healthy link with increasing receive counters but no reply moves the decision toward relay addressing or service configuration. No receive-count change while the client transmits points back toward the switch path, VLAN, or destination addressing.
How should the resolving change be applied and verified?
- Read the T60 option code and identify whether the Ethernet interface is copper or fiber and whether it supports
10 Mbps,100 Mbps, or both. - Inspect the switch port media and confirm that it matches the installed relay interface.
- Remove the known duplex conflict. Configure both ends for the same supported duplex mode, or use compatible automatic behavior on both ends.
- Configure a common supported speed. Select
100 Mbpsonly for a confirmed capable option; otherwise use10 Mbps. - Confirm stable link indication, record or clear the switch counters, and generate client traffic.
- Verify that physical errors and collision symptoms do not increase during the test.
- Confirm the relay IP address and test IP reachability from the actual client path.
- Open the required application session and verify repeated request-and-response exchanges without intermittent loss or timeout.
FAQ
Can I set the T60 switch port to 100 Mbps?
Yes, when the installed Ethernet option is confirmed to support 100 Mbps. If it is not 100 Mbps capable, configure the switch for 10 Mbps.
Can I leave the switch at half duplex when the relay is full duplex?
No. Match the duplex settings or configure compatible automatic behavior on both ends; the half/full mismatch can cause loss, retries, and intermittent communication.
Does every T60 relay have the same Ethernet port?
No. Identify the installed option from the relay option code, manual, and rear hardware; possible interfaces include serial and copper or fiber Ethernet combinations.
Does a link light prove T60 communication is fixed?
No. After confirming the link, verify that switch error counters remain stable, the configured relay IP address is reachable from the real client path, and repeated application requests receive responses without timeout.