LAN speed drops to 100Mbps after updating to OPNsense 25.1.9_2 [SOLVED]

[NajibHassan]

Hi all,

After updating to OPNsense 25.1.9_2-amd64, I noticed that my LAN speed dropped significantly. I ran an iperf3 test from my PC to the OPNsense firewall, and the result was consistently around 93–94 Mbps, indicating a fallback to 100Mbps speeds.

Before the update, the same setup (PC ↔ OPNsense) was running at full Gigabit speed. I have confirmed the following:
   •   Interface re0 shows 1000baseT <full-duplex> and status active.
   •   I am using a Realtek NIC (device ID 0x8168).
   •   Cables and switches are all Gigabit-capable.
   •   iperf3 from the same PC to another PC on the network gives ~900 Mbps consistently.
   •   I installed the os-realtek-re plugin and rebooted. The driver is loaded (if_re.ko), but iperf3 to the OPNsense box still gives ~93 Mbps.
   •   I am using PPPoE for WAN connection — not sure if that contributes to the performance drop.

Is this a known issue introduced in 25.1.9_2? Could PPPoE be affecting internal LAN performance or loopback traffic in this version?

Any insights or suggested tunables would be appreciated.

Thanks!

[sorano]

May I suggest tunable replacing realteak with Intel NIC.

[NajibHassan]

Update: The issue is now resolved. It turned out that my switch was starting to fail — although link lights were on, it silently dropped back to 100Mbps. Today, the switch completely died, and after replacing it with a new Gigabit switch, the LAN speed immediately returned to normal (~900 Mbps via iperf3).

Thanks to everyone who read or considered the issue. Hopefully this helps someone else troubleshooting similar symptoms.