What This Guide Covers

This guide explains how to resolve a situation where a Dell PowerSwitch S5224F-ON detects an SFP module and shows the physical interface as up, but the line protocol remains down when connecting to a 10Gb link, such as a switch from another vendor. It also covers the required port-group configuration for 10Gb operation on supported ports.

Quick Fix Summary

Configure the affected port group to operate in 10Gb breakout mode using mode Eth 10g-4x.
After changing the port-group mode, use the newly created breakout interfaces for configuration.
Verify speed and compatibility settings on both connected switches and confirm the link is operating at the same speed.

On Dell PowerSwitch platforms running OS10, a 25Gb-capable port may detect an inserted transceiver while still reporting:

Ethernet interface is up, line protocol is down

This can occur when a 25Gb port is connected to a 10Gb device without the appropriate port-group configuration. In these cases, the physical transceiver is recognized, but the operational link cannot be established until the port is configured for 10Gb operation.

Error Indicators

Common symptoms include:

Interface status displays:

Ethernet 1/1/17 is up, line protocol is down

Transceiver is recognized by the switch.
No traffic passes across the link.
Interface reports:
```
LineSpeed 0
```
Auto-negotiation changes do not bring the link up.

Possible Causes

A 25Gb port is connected to a 10Gb device without converting the port group to 10Gb mode.
Port-group settings do not match the required breakout configuration.
Speed configuration differs between the connected devices.
The interface being configured is not the active breakout interface after a port-group conversion.

Troubleshooting Steps

1. Configure the Port Group for 10Gb Operation (Confirmed Fix)

On the affected port, configure the port group as follows:

OS10(config)# port-group 1/1/17

OS10(conf-pg-1/1/17)# mode Eth 10g-4x

This configuration enables 10Gb operation on the supported port group and was confirmed to bring the protocol state up. [dell.com]

2. Use the Correct Breakout Interface

After the port group is converted, the original interface may no longer be directly configurable.

Configure the breakout interface instead:

OS10(config)# interface ethernet 1/1/17:1

The breakout interface becomes the configuration point for VLAN, trunk, and other interface settings.

3. Verify Interface Status

Confirm that the interface is operational:

show interface ethernet 1/1/17:1

Verify that:

The link is detected.
The line protocol is up.
Speed and operational parameters match the connected device.

4. Configure Inter-Switch Connectivity

After the link is operational:

Configure VLANs as required.
Configure trunking on the Dell interface.
Ensure VLAN membership and trunk settings match on both switches.
If link aggregation is used, verify compatible LAG/LACP settings on both devices.

5. Validate End-to-End Connectivity

Test connectivity by:

Checking interface counters.
Verifying VLAN propagation.
Testing network reachability across the fiber link.
Confirming that traffic is passing successfully between switches.

Additional Notes

Some S5224F-ON ports support multiple operating modes and may require explicit port-group configuration when connecting to lower-speed devices.
After changing port-group modes, interface numbering and configuration methods may change to breakout-style interfaces (for example, 1/1/17:1).
Always verify transceiver compatibility and supported speeds before deploying inter-switch links.

References

Original Dell Community discussion:
https://www.dell.com/community/en/conversations/networking-general/ethernet-1117-is-up-line-protocol-is-down-with-sfp-10g-os10/66222f04a97a0a68c376c300 [dell.com]
Dell OS10 Networking Documentation (referenced in the discussion for port-group and inter-switch configuration guidance). ‎Ethernet 1/1/17 is up, line protocol is down with SFP 10G OS10 | DELL Technologies

Affected Systems

Dell Hardware

Dell PowerSwitch S5224F-ON Support for PowerSwitch S5224F-ON | Overview | Dell US

Operating System

Dell SmartFabric OS10 (OS10) Support for SmartFabric OS10 Software | Overview | Dell US

Connection Scenarios

25Gb Dell switch ports connected to 10Gb Ethernet devices.
Fiber optic inter-switch links using SFP/SFP28 transceivers.
Mixed-vendor network environments requiring 10Gb connectivity. [dell.com]

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