Re: rge(4) RTL8125 2.5GbE testing: 2500baseT media type not available on 16.0-CURRENT

In reply to: Adrian Chadd : "Re: rge(4) RTL8125 2.5GbE testing: 2500baseT media type not available on 16.0-CURRENT"
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From: Olivier_Cochard-Labbé <olivier_at_freebsd.org>
Date: Fri, 06 Mar 2026 16:39:32 UTC

On Fri, Mar 6, 2026 at 5:00 PM Adrian Chadd <adrian@freebsd.org> wrote:

> On Thu, 5 Mar 2026 at 14:02, Olivier Cochard-Labbé <olivier@freebsd.org>
> wrote:
>
> > It shows a negotiated speed of 2.5G:
> >
> [snip]
>
> > However, I am experiencing the same 100Mb/s (yes 100) limitation that
> occurred on both Ubuntu (with both the default r8169 and official Realtek
> r8125 driver) and Windows:
> > Despite the reported link speed, the actual throughput is capped 100Mb/s:
> >
> > olivier@fbsd:~$ iperf3 -c 192.168.100.1
> > (...)
> > - - - - - - - - - - - - - - - - - - - - - - - - -
> > [ ID] Interval           Transfer     Bitrate         Retr
> > [  5]   0.00-10.06  sec   113 MBytes  94.3 Mbits/sec    0
> sender
> > [  5]   0.00-10.08  sec   113 MBytes  94.1 Mbits/sec
> receiver
>
> Is it 100mbit when you neg at 1gbit? or only at 2.5g?
>
>
Oops!
While replacing the 2.5Gb switch with a 1G switch for your test, I noticed
a non-compliant Ethernet cable in the uplink (between the switches).
After fixing this, the 2.5Gb performance is now as expected:

olivier@freebsd:~ $ iperf3 -c 192.168.100.1
Connecting to host 192.168.100.1, port 5201
[  5] local 192.168.100.161 port 35882 connected to 192.168.100.1 port 5201
[ ID] Interval           Transfer     Bitrate         Retr  Cwnd
[  5]   0.00-1.06   sec   300 MBytes  2.37 Gbits/sec    0   1.60 MBytes
[  5]   1.06-2.06   sec   280 MBytes  2.35 Gbits/sec    0   1.60 MBytes
[  5]   2.06-3.00   sec   264 MBytes  2.35 Gbits/sec    0   1.60 MBytes
[  5]   3.00-4.00   sec   281 MBytes  2.35 Gbits/sec    0   1.60 MBytes
[  5]   4.00-5.00   sec   280 MBytes  2.35 Gbits/sec    0   1.60 MBytes
[  5]   5.00-6.06   sec   298 MBytes  2.35 Gbits/sec    0   1.60 MBytes
[  5]   6.06-7.04   sec   275 MBytes  2.35 Gbits/sec    0   1.60 MBytes
[  5]   7.04-8.00   sec   268 MBytes  2.35 Gbits/sec    0   1.60 MBytes
[  5]   8.00-9.00   sec   281 MBytes  2.35 Gbits/sec    0   1.60 MBytes
[  5]   9.00-10.00  sec   281 MBytes  2.35 Gbits/sec    0   1.60 MBytes
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bitrate         Retr
[  5]   0.00-10.00  sec  2.74 GBytes  2.36 Gbits/sec    0            sender
[  5]   0.00-10.01  sec  2.74 GBytes  2.35 Gbits/sec
 receiver

iperf Done.

Apologies for this oversight.
Regards,

Olivier