If ZimaBlade negotiates only 100Mbps, troubleshoot the Ethernet link before testing SMB, disks, or ZimaOS tuning. Gigabit Ethernet requires all four twisted pairs, clean connector contacts, a gigabit-capable switch port, and successful auto-negotiation. Forcing 1Gbps is not a reliable fix.
The 2026 source case showed ethtool reporting exactly 100Mb/s full duplex with auto-negotiation on. Current ZimaBlade specifications list one Gigabit Ethernet port, so a persistent 100Mbps link is below the hardware's intended link speed and should be isolated systematically.
Confirm the Negotiated Link Speed
ip link
ethtool eth0Replace eth0 with your actual interface. Check Speed, Duplex, Auto-negotiation, and Link detected.
Do Not Use SMB Speed as the First Test
5–6MB/s could be caused by a 100Mbps link, Wi-Fi, slow storage, encryption, or the client. First confirm the physical Ethernet negotiation.
Test a Short Known-Good Cat5e/Cat6 Cable
Connect ZimaBlade directly to a known gigabit router/switch port. Bypass wall jacks, couplers, patch panels, and long in-wall runs.
Gigabit needs four pairs; 100Mbps can continue working when only two pairs are functional.
Try Another Switch Port and Link Partner
A damaged or forced-speed switch port can hold the link at 100Mbps. Test a different switch/router and restore both ends to normal auto-negotiation.
Check Advertised Link Modes
In ethtool, compare Supported, Advertised, and Link partner advertised modes. If the ZimaBlade advertises 1000baseT/Full but the partner only negotiates 100, the physical path or link partner remains suspect.
Why Forcing 1Gbps Can Drop the Link
1000BASE-T depends on auto-negotiation for master/slave and other parameters. A marginal cable that can carry 100Mbps may fail completely when forced toward gigabit operation.
Current Hardware Specification
The current ZimaBlade hardware guide lists one Gigabit Ethernet port for both current ZimaBlade variants.
When to Suspect Hardware Failure
If multiple known-good short cables, multiple gigabit switches, clean connectors, and normal auto-negotiation all result in exactly 100Mbps, the onboard Ethernet jack, magnetics, or NIC path becomes a reasonable hardware suspect.
The hardware troubleshooting guide gives a broader escalation checklist.
Use iperf3 After the Link Reaches 1Gbps
Once ethtool reports 1000Mb/s, test raw network throughput before judging Samba performance. An iperf3 test between ZimaBlade and a wired LAN computer removes disk speed and filesystem overhead from the measurement.
On a healthy Gigabit Ethernet path, real TCP throughput should be far above a 100Mbps-class result. If iperf is fast but file copies are slow, move to storage and SMB diagnostics.
Check for Link Errors and Retransmission Clues
Use:
ip -s link show eth0
ethtool -S eth0Look for increasing receive/transmit errors, CRC-related counters, or repeated link resets. A connection can negotiate at Gigabit yet perform badly when the physical path is marginal.
Do Not Overlook Wall Cabling
A short patch cable can test perfectly while a wall jack or punch-down connection has one broken pair. Because 100BASE-TX needs only two pairs but 1000BASE-T needs all four, a building cable fault often presents as a stable 100Mbps link rather than total disconnection.
Separate Wi-Fi from Ethernet Tests
The source discussion also included a user who thought Samba was slow over Ethernet but was actually connected over Wi-Fi. Check the active interface and route before comparing throughput numbers.
FAQ
What throughput should 100Mbps Ethernet give?
Real file-transfer speeds are commonly around 10–12MB/s at best after protocol overhead, not 100MB/s.
Why can a bad cable still work at 100Mbps?
Fast Ethernet uses fewer wire pairs than Gigabit Ethernet, so partial cable faults can still permit a 100Mbps link.
Should I force 1000baseT?
No. Keep normal auto-negotiation while isolating cable, switch, and NIC behavior.
What if ethtool says 1Gbps but SMB is slow?
Then move up the stack and test disk throughput, client networking, Wi-Fi, SMB settings, and application paths separately.
