OPNSense inexplicably dropping down to 100Mbps from 1Gbps on WAN interface

[Shoresy]

I've noticed, since installing/configuring my OPNsense box, that it has been inexplicably dropping my WAN throughput from 1Gbps to 100Mbps. It has done this twice in the past 24 hours. Rebooting the OPNsense box returns things to normal.

I've since turned off autosense on the interfaces and set them all to 1000Mbps Full Duplex - I did this for both WAN interfaces plus the LAN interface. However, the interface status would still show 1000Mbps full Duplex when this 100Mbs throughput throttling issue occurred. "Disable hardware offload" boxes are all checked off within Interfaces > Settings. I have yet to see if this issue reoccurs after making these changes, but am skeptical at this point.

Has anyone encountered this odd behavior and resolved it? I can't figure out why everything would run perfectly fine at 1Gbps and hours later throttle down to 100Mbps. I've tested all my Cat6 patch cables and there are no issues with them. OPNsense version and hardware specs are in my signature as a FYI.

Edit: I figured this problem out and it wasn't related to OPNsense. One of my EAP's was the culprit...a 2.5Gbe port not negotiating correctly with a 1000Mbps managed switch. It was initially negotiating 1000Mbps full duplex, but reverting to 100Mbps about 10 minutes later. Changing switches fixed the problem.

[eneerge]

I just posted this same issue.

What did you mean by dupe? Did you find another post where this happened (duplicate)?

[Shoresy]

I accidentally posted the same message twice, so I deleted the reply. This happened when I first set up OPNsense, and found that one of my Wifi EAP's was negotiating at 100Mbps which was somehow propagating down to the router. After figuring out the issue with the EAP (the EAP's 2.5Gbe port wasn't negotiating properly with a dummy switch), I removed the switch and the issue went away. I haven't observed the router dropping my network speed since removing the dummy switch (which was a 1Gb switch).

Definitely check your patch cables, switches, and any other devices you might have connected to your network. Eventually you'll isolate the issue...patch cables are usually the #1 culprit. Even if they test out ok a lengthy patch cable may fail to negotiate at 1Gbps and may cause the router to negotiate at the lower network speed.

You can try setting your WAN interface to 1000Mbps full duplex in Interfaces > [Your WAN here]. If you can set the speed/duplex on the port used by the ISP's modem or network terminal, set it to 1000mbps full duplex there as well.