我使用的是 Ubuntu 22.04.4 LTS，主板上有 RTL8125，Windows 10 工作站配有 SD-PEX24066 NIC，使用相同的 RTL8125 芯片组，交换机是 QNAP QSW-1105-5T。我已通过 netplan 将 MTU 设置为 9000，配置在启动时设置为 9000。我没有获得我期望的速度，Ubuntu 报告了相互矛盾的信息。
这是双向 iperf（无论谁是服务器/客户端，速度都相似）：
乌本图：
~# iperf3 -c 192.168.1.175 -bidir
Connecting to host 192.168.1.175, port 5201
[ 5] local 192.168.1.174 port 57786 connected to 192.168.1.175 port 5201
[ ID] Interval Transfer Bitrate Retr Cwnd
[ 5] 0.00-1.00 sec 195 MBytes 1.64 Gbits/sec 0 158 KBytes
[ 5] 1.00-2.00 sec 198 MBytes 1.66 Gbits/sec 0 158 KBytes
[ 5] 2.00-3.00 sec 179 MBytes 1.50 Gbits/sec 0 158 KBytes
[ 5] 3.00-4.00 sec 165 MBytes 1.38 Gbits/sec 0 158 KBytes
[ 5] 4.00-5.00 sec 165 MBytes 1.38 Gbits/sec 0 158 KBytes
[ 5] 5.00-6.00 sec 165 MBytes 1.39 Gbits/sec 0 158 KBytes
[ 5] 6.00-7.00 sec 165 MBytes 1.38 Gbits/sec 0 158 KBytes
[ 5] 7.00-8.00 sec 165 MBytes 1.38 Gbits/sec 0 158 KBytes
[ 5] 8.00-9.00 sec 165 MBytes 1.38 Gbits/sec 0 158 KBytes
[ 5] 9.00-10.00 sec 165 MBytes 1.38 Gbits/sec 0 158 KBytes
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval Transfer Bitrate Retr
[ 5] 0.00-10.00 sec 1.69 GBytes 1.45 Gbits/sec 0 sender
[ 5] 0.00-10.00 sec 1.69 GBytes 1.45 Gbits/sec receiver
视窗：
Accepted connection from 192.168.1.174, port 57776
[ 5] local 192.168.1.175 port 5201 connected to 192.168.1.174 port 57786
[ ID] Interval Transfer Bandwidth
[ 5] 0.00-1.00 sec 188 MBytes 1.57 Gbits/sec
[ 5] 1.00-2.00 sec 198 MBytes 1.66 Gbits/sec
[ 5] 2.00-3.00 sec 179 MBytes 1.51 Gbits/sec
[ 5] 3.00-4.00 sec 165 MBytes 1.39 Gbits/sec
[ 5] 4.00-5.00 sec 165 MBytes 1.39 Gbits/sec
[ 5] 5.00-6.00 sec 165 MBytes 1.39 Gbits/sec
[ 5] 6.00-7.00 sec 165 MBytes 1.38 Gbits/sec
[ 5] 7.00-8.00 sec 165 MBytes 1.39 Gbits/sec
[ 5] 8.00-9.00 sec 165 MBytes 1.39 Gbits/sec
[ 5] 9.00-10.00 sec 165 MBytes 1.38 Gbits/sec
[ 5] 10.00-10.04 sec 5.74 MBytes 1.38 Gbits/sec
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval Transfer Bandwidth
[ 5] 0.00-10.04 sec 0.00 Bytes 0.00 bits/sec sender
[ 5] 0.00-10.04 sec 1.69 GBytes 1.44 Gbits/sec receiver
Ubuntu NIC 显示的额定速度信息相互矛盾，不知道该相信什么：
~# ip link show
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1000
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
2: enp42s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 9000 qdisc fq_codel state UP mode DEFAULT group default qlen 1000
link/ether 2c:f0:5d:7c:91:20 brd ff:ff:ff:ff:ff:ff
~# inxi -n
Network:
Device-1: Realtek RTL8125 2.5GbE driver: r8169
IF: enp42s0 state: up speed: 2500 Mbps duplex: full mac: 2c:f0:5d:7c:91:20
~# lshw -class network
*-network
description: Ethernet interface
product: RTL8125 2.5GbE Controller
vendor: Realtek Semiconductor Co., Ltd.
physical id: 0
bus info: pci@0000:2a:00.0
logical name: enp42s0
version: 04
serial: 2c:f0:5d:7c:91:20
capacity: 1Gbit/s
width: 64 bits
clock: 33MHz
capabilities: pm msi pciexpress msix vpd bus_master cap_list ethernet physical tp mii 10bt 10bt-fd 100bt 100bt-fd 1000bt-fd autonegotiation
configuration: autonegotiation=on broadcast=yes driver=r8169 driverversion=5.15.0-97-generic duplex=full firmware=rtl8125b-2_0.0.2 07/13/20 ip=192.168.1.174 latency=0 link=yes multicast=yes port=twisted pair
resources: irq:35 ioport:f000(size=256) memory:fc500000-fc50ffff memory:fc510000-fc513fff
~# mii-tool -v enp42s0
enp42s0: negotiated 1000baseT-FD flow-control, link ok
product info: vendor 00:e0:4c or 00:07:32, model 4 rev 0
basic mode: autonegotiation enabled
basic status: autonegotiation complete, link ok
capabilities: 1000baseT-FD 100baseTx-FD 100baseTx-HD 10baseT-FD 10baseT-HD
advertising: 1000baseT-FD 100baseTx-FD 100baseTx-HD 10baseT-FD 10baseT-HD
link partner: 1000baseT-HD 1000baseT-FD 100baseTx-FD 100baseTx-HD 10baseT-FD 10baseT-HD flow-control
~# ethtool enp42s0
Settings for enp42s0:
Supported ports: [ TP MII ]
Supported link modes: 10baseT/Half 10baseT/Full
100baseT/Half 100baseT/Full
1000baseT/Full
2500baseT/Full
Supported pause frame use: Symmetric Receive-only
Supports auto-negotiation: Yes
Supported FEC modes: Not reported
Advertised link modes: 10baseT/Half 10baseT/Full
100baseT/Half 100baseT/Full
1000baseT/Full
2500baseT/Full
Advertised pause frame use: No
Advertised auto-negotiation: Yes
Advertised FEC modes: Not reported
Link partner advertised link modes: 10baseT/Half 10baseT/Full
100baseT/Half 100baseT/Full
1000baseT/Half 1000baseT/Full
2500baseT/Full
Link partner advertised pause frame use: Symmetric Receive-only
Link partner advertised auto-negotiation: Yes
Link partner advertised FEC modes: Not reported
Speed: 2500Mb/s
Duplex: Full
Auto-negotiation: on
master-slave cfg: preferred slave
master-slave status: slave
Port: Twisted Pair
PHYAD: 0
Transceiver: external
MDI-X: Unknown
Supports Wake-on: pumbg
Wake-on: d
Link detected: yes
Windows 工作站具有巨型帧、2.5G 全双工、启用大型发送卸载以及接收/发送缓冲区为 512 等功能。它显示 MTU 为 9198：
>netsh interface ipv4 show subinterface
MTU MediaSenseState Bytes In Bytes Out Interface
------ --------------- --------- --------- -------------
9198 1 nnn nnn Ethernet
有谁知道为什么 Ubuntu 服务器显示冲突的信息以及我缺少什么才能达到全速？