Data Domain: Bonded Interface Alert Due to Member Interface Speed Mismatch
Summary: A bonded interface speed mismatch alert may occur when one member interface negotiates at a lower speed than the other member interfaces in the bond. This causes the alert to remain active until all interfaces operate at the same speed. ...
Symptoms
Current Alerts:
-------------- Id Post Time Severity Class Object Message ------- ------------------------ -------- ------- --------------------------- -------------------------------------------- p0-1501 Wed 04:41:42 2026 CRITICAL Network Bonded Interface Name=veth0 EVT-NETM-00015: One or more interfaces in the bonded group has a speed mismatch. ------- ------------------------ -------- ------- --------------------------- -------------------------------------------- There is 1 active alert. No recent alerts noted in logs.
Bonded interface remains operational, but a critical network alert is reported.
No related alerts may be present in recent logs.
One bond member may be running at a different negotiated speed than the other bond members.
Example of the mismatch:
eth2c = 10Gb/s
eth2d = 25Gb/s
The affected interfaces are members of the same bonded interface (veth0).
Cause
The alert is generated when member interfaces within a bonded interface are running at different link speeds.
Although a support bundle may show all interfaces operating at the same speed at a given point in time, later AutoSupport or Elysium data may indicate that one interface has negotiated a lower speed. In this case, interface eth2c was operating at 10Gb/s while eth2d was operating at 25Gb/s, causing the speed mismatch alert for bond veth0.
The alert persists until all member interfaces within the bond are running at the same speed.
Historically, this issue has most commonly been caused by:
- Faulty or degraded network cable
- Optical connectivity issues
- Transceiver/SFP issues
- Switch port configuration mismatches
- Switch-side speed negotiation problems
The issue has been observed on both copper and SFP-based connections.
- Mixed speed interfaces configured within the same bond (for example, one member operating at 1 GbE while another operates at 10 GbE or 25 GbE).
- Auto-negotiation mismatches causing interfaces to negotiate at different speeds.
- Incorrect manual speed or duplex configuration on one or more bond members.
- Switch-side configuration issues where member interfaces are connected to ports configured for different speeds.
- Hardware compatibility or transceiver-related issues resulting in one interface negotiating below the expected speed.
- Damaged or degraded copper, fiber, or Direct Attach (DA) copper cabling.
Faulty or marginal SFP/QSFP transceivers. - Incorrect patch panel connections or cables connected to the wrong switch ports.
- In environments using 1 GbE networking, cable quality and cable length may impact successful auto-negotiation. If both switch and Data Domain interfaces are configured for auto-negotiation, poor cable quality or excessive cable length may cause an interface to negotiate below the expected speed.
Beginning with DDOS 7.9, Data Domain introduced additional validation and alerting for bonded interfaces with member speed mismatches. Customers upgrading to newer DDOS releases may begin seeing alerts for pre-existing network configuration issues that were previously not reported. If member interfaces operate at different speeds, failover behavior may not function as expected and some switch platforms may place affected ports into a suspended state.
Resolution
Example of troubleshooting steps:
(Using virtual interface zero with interfaces ethernet two c)
Verify the speed of all member interfaces:
net show settings
net show hardware
- If one interface is operating below the expected speed, attempt to statically configure the interface for the desired speed.
- Remove the Interface from the Bond
net failover del veth0 interfaces eth2c
-
- Configure the Interface for 25Gb/s
net config eth2c speed 25000
-
- Bring the Interface Up
net config eth2c up
-
- Verify the Interface Speed and Status
net show settings
net show hardware
- If eth2c successfully comes online at 25Gb/s, add it back into the bonded interface.
- Bring the Interface Down
net config eth2c down
-
- Add the Interface Back to the Bond
net failover add veth0 interfaces eth2c
-
- Verify Bond Configuration
net failover show
-
- Verify Both Interfaces Are Operating at 25Gb/s
net show settings
net show hardware
Additional troubleshooting:
Reinitialize the Interface and Verify Negotiation
- If the affected interface is not negotiating at the expected speed:
- Disable and re-enable the interface.
net disable ethXx
net enable ethXx
-
- Verify negotiated speed:
net show hardware
- If the interface supports auto-negotiation:
- Configure auto-negotiation and verify the resulting speed:
net config ethXx autoneg
-
- Verify speed again:
net show hardware
- If required by the network design
- Manually configure speed and duplex settings:
Example net config eth8a duplex full speed 100000
-
- Verify that the interface negotiates successfully and that all members of the bond operate at the same speed.
Verify Cabling and Connectivity Path
Speed mismatches are commonly caused by connectivity issues external to the Data Domain. Perform the following checks:
- Verify cables are connected to the correct switch ports.
- Verify switch ports assigned to bond members are configured identically.
- Reseat cables and transceivers on both the Data Domain and switch sides.
- Swap cables between a known-good interface and the affected interface.
Cable swapping can be performed for:
- Direct Attach (DA) copper cables
- Fiber optic connections
- Traditional copper Ethernet cables
If the speed mismatch follows the cable, the issue is likely cabling, optics, or switch-port related.
Replace Connectivity Components
If the interface continues to negotiate at a lower speed after switch configuration has been verified, replace suspect components in the connectivity path. Potential components to replace include:
- Copper Ethernet cable
- Direct Attach (DA) cable
- Fiber optic cable
- SFP/SFP+/SFP28/QSFP transceiver on the switch side
- SFP/SFP+/SFP28/QSFP transceiver on the Data Domain side
Escalation Information
If the issue persists after completing the troubleshooting steps above, contact Dell Support after collectIng:
net show hardware net show settings alerts show current alerts show history
and also gathering:
- Latest support bundle
- Switch make and model
- Switch operating system version
- Switch port configuration
- Port speed and duplex settings
- Transceiver details
- Cable type (Copper, Fiber, DA Copper)
- Confirmation of any cable or transceiver swaps performed
This information can help determine whether the issue is related to Data Domain hardware, switch configuration, connectivity components, or interface negotiation behavior.