[SOLVED] I can't get my RTL8125BG network card to work on Proxmox, in any way.

A

Alenygam

New Member
Jul 28, 2025
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Hi! I write this post as a last resort.

I'm trying to get a quad port RTL8125BG based network card I got for cheap to work on Proxmox VE, or really any other Linux OS. The network card works perfectly on Windows (Bare Metal), but when I try to run it in Proxmox VE (and I also tried Fedora bare metal), I get spammed with NETDEV WATCHDOG: CPU: 1: transmit queue 0 timed out 5202ms. I spent more than 10 hours trying all kinds of different configurations: older kernel (6.5), newest kernel (6.14), other distros (Fedora), out-of tree drivers (r8125, I tried this on all the previous configs), but I can't seem to get this network card to work at all in Linux.

Here's the dmesg | grep -i r8169 output:
Code: 
[    2.189722] r8169 0000:05:00.0 eth0: RTL8168h/8111h, 24:4b:fe:52:7a:a2, XID 541, IRQ 42
[    2.189729] r8169 0000:05:00.0 eth0: jumbo features [frames: 9194 bytes, tx checksumming: ko]
[    2.189765] r8169 0000:08:00.0: enabling device (0000 -> 0003)
[    2.196909] r8169 0000:08:00.0 eth1: RTL8125B, 7e:db:75:e7:e6:e0, XID 641, IRQ 44
[    2.196913] r8169 0000:08:00.0 eth1: jumbo features [frames: 9194 bytes, tx checksumming: ko]
[    2.196936] r8169 0000:09:00.0: enabling device (0000 -> 0003)
[    2.204061] r8169 0000:09:00.0 eth2: RTL8125B, 00:e0:4c:68:06:47, XID 641, IRQ 46
[    2.204065] r8169 0000:09:00.0 eth2: jumbo features [frames: 9194 bytes, tx checksumming: ko]
[    2.204088] r8169 0000:0a:00.0: enabling device (0000 -> 0003)
[    2.210778] r8169 0000:0a:00.0 eth3: RTL8125B, 00:e0:4c:68:06:48, XID 641, IRQ 48
[    2.210782] r8169 0000:0a:00.0 eth3: jumbo features [frames: 9194 bytes, tx checksumming: ko]
[    2.210804] r8169 0000:0b:00.0: enabling device (0000 -> 0003)
[    2.217707] r8169 0000:0b:00.0 eth4: RTL8125B, 00:e0:4c:68:06:49, XID 641, IRQ 50
[    2.217711] r8169 0000:0b:00.0 eth4: jumbo features [frames: 9194 bytes, tx checksumming: ko]

Here is the ethtool enp9s0 output (enp9s0 is one of the 4 ports of my nic, the others are analogous):
Code: 
Settings for enp9s0:
        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: Symmetric Receive-only
        Advertised auto-negotiation: Yes
        Advertised FEC modes: Not reported
        Link partner advertised link modes:  10baseT/Half 10baseT/Full
                                             100baseT/Half 100baseT/Full
                                             1000baseT/Full
        Link partner advertised pause frame use: Symmetric Receive-only
        Link partner advertised auto-negotiation: Yes
        Link partner advertised FEC modes: Not reported
        Speed: 1000Mb/s
        Duplex: Full
        Auto-negotiation: on
        master-slave cfg: preferred slave
        master-slave status: slave
        Port: Twisted Pair
        PHYAD: 0
        Transceiver: internal
        MDI-X: Unknown
        Supports Wake-on: pumbg
        Wake-on: d
        Link detected: yes
The partner isn't advertising 2500baseT/Full because it's my laptop, that doesn't have a 2.5 gigabit network card.

Here is the relevant lspci -nnv output:
Code: 
08:00.0 Ethernet controller [0200]: Realtek Semiconductor Co., Ltd. RTL8125 2.5GbE Controller [10ec:8125] (rev 05)
        Subsystem: Realtek Semiconductor Co., Ltd. RTL8125 2.5GbE Controller [10ec:8125]
        Flags: fast devsel, IRQ 43, IOMMU group 20
        I/O ports at d000 [size=256]
        Memory at fc900000 (64-bit, non-prefetchable) [size=64K]
        Memory at fc910000 (64-bit, non-prefetchable) [size=16K]
        Capabilities: [40] Power Management version 3
        Capabilities: [50] MSI: Enable- Count=1/1 Maskable+ 64bit+
        Capabilities: [70] Express Endpoint, MSI 01
        Capabilities: [b0] MSI-X: Enable+ Count=32 Masked-
        Capabilities: [d0] Vital Product Data
        Capabilities: [100] Advanced Error Reporting
        Capabilities: [148] Virtual Channel
        Capabilities: [168] Device Serial Number 01-00-00-00-68-4c-e0-00
        Capabilities: [178] Transaction Processing Hints
        Capabilities: [204] Latency Tolerance Reporting
        Capabilities: [20c] L1 PM Substates
        Capabilities: [21c] Vendor Specific Information: ID=0002 Rev=4 Len=100 <?>
        Kernel driver in use: r8169
        Kernel modules: r8169, r8125

09:00.0 Ethernet controller [0200]: Realtek Semiconductor Co., Ltd. RTL8125 2.5GbE Controller [10ec:8125] (rev 05)
        Subsystem: Realtek Semiconductor Co., Ltd. RTL8125 2.5GbE Controller [10ec:8125]
        Flags: bus master, fast devsel, latency 0, IRQ 45, IOMMU group 21
        I/O ports at c000 [size=256]
        Memory at fc800000 (64-bit, non-prefetchable) [size=64K]
        Memory at fc810000 (64-bit, non-prefetchable) [size=16K]
        Capabilities: [40] Power Management version 3
        Capabilities: [50] MSI: Enable- Count=1/1 Maskable+ 64bit+
        Capabilities: [70] Express Endpoint, MSI 01
        Capabilities: [b0] MSI-X: Enable+ Count=32 Masked-
        Capabilities: [d0] Vital Product Data
        Capabilities: [100] Advanced Error Reporting
        Capabilities: [148] Virtual Channel
        Capabilities: [168] Device Serial Number 01-00-00-00-68-4c-e0-00
        Capabilities: [178] Transaction Processing Hints
        Capabilities: [204] Latency Tolerance Reporting
        Capabilities: [20c] L1 PM Substates
        Capabilities: [21c] Vendor Specific Information: ID=0002 Rev=4 Len=100 <?>
        Kernel driver in use: r8169
        Kernel modules: r8169, r8125

0a:00.0 Ethernet controller [0200]: Realtek Semiconductor Co., Ltd. RTL8125 2.5GbE Controller [10ec:8125] (rev 05)
        Subsystem: Realtek Semiconductor Co., Ltd. RTL8125 2.5GbE Controller [10ec:8125]
        Flags: fast devsel, IRQ 47, IOMMU group 22
        I/O ports at b000 [size=256]
        Memory at fc700000 (64-bit, non-prefetchable) [size=64K]
        Memory at fc710000 (64-bit, non-prefetchable) [size=16K]
        Capabilities: [40] Power Management version 3
        Capabilities: [50] MSI: Enable- Count=1/1 Maskable+ 64bit+
        Capabilities: [70] Express Endpoint, MSI 01
        Capabilities: [b0] MSI-X: Enable+ Count=32 Masked-
        Capabilities: [d0] Vital Product Data
        Capabilities: [100] Advanced Error Reporting
        Capabilities: [148] Virtual Channel
        Capabilities: [168] Device Serial Number 01-00-00-00-68-4c-e0-00
        Capabilities: [178] Transaction Processing Hints
        Capabilities: [204] Latency Tolerance Reporting
        Capabilities: [20c] L1 PM Substates
        Capabilities: [21c] Vendor Specific Information: ID=0002 Rev=4 Len=100 <?>
        Kernel driver in use: r8169
        Kernel modules: r8169, r8125

0b:00.0 Ethernet controller [0200]: Realtek Semiconductor Co., Ltd. RTL8125 2.5GbE Controller [10ec:8125] (rev 05)
        Subsystem: Realtek Semiconductor Co., Ltd. RTL8125 2.5GbE Controller [10ec:8125]
        Flags: fast devsel, IRQ 49, IOMMU group 23
        I/O ports at a000 [size=256]
        Memory at fc600000 (64-bit, non-prefetchable) [size=64K]
        Memory at fc610000 (64-bit, non-prefetchable) [size=16K]
        Capabilities: [40] Power Management version 3
        Capabilities: [50] MSI: Enable- Count=1/1 Maskable+ 64bit+
        Capabilities: [70] Express Endpoint, MSI 01
        Capabilities: [b0] MSI-X: Enable+ Count=32 Masked-
        Capabilities: [d0] Vital Product Data
        Capabilities: [100] Advanced Error Reporting
        Capabilities: [148] Virtual Channel
        Capabilities: [168] Device Serial Number 01-00-00-00-68-4c-e0-00
        Capabilities: [178] Transaction Processing Hints
        Capabilities: [204] Latency Tolerance Reporting
        Capabilities: [20c] L1 PM Substates
        Capabilities: [21c] Vendor Specific Information: ID=0002 Rev=4 Len=100 <?>
        Kernel driver in use: r8169
        Kernel modules: r8169, r8125

Here's the output of ip a
Code: 
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host noprefixroute
       valid_lft forever preferred_lft forever
2: enp5s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast master vmbr0 state UP group default qlen 1000
    link/ether 24:4b:fe:52:7a:a2 brd ff:ff:ff:ff:ff:ff
3: enp8s0: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN group default qlen 1000
    link/ether 7e:db:75:e7:e6:e0 brd ff:ff:ff:ff:ff:ff
4: enp9s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast master vmbr1 state UP group default qlen 1000
    link/ether 00:e0:4c:68:06:47 brd ff:ff:ff:ff:ff:ff
5: enp10s0: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN group default qlen 1000
    link/ether 00:e0:4c:68:06:48 brd ff:ff:ff:ff:ff:ff
6: enp11s0: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN group default qlen 1000
    link/ether 00:e0:4c:68:06:49 brd ff:ff:ff:ff:ff:ff
7: vmbr0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
    link/ether 24:4b:fe:52:7a:a2 brd ff:ff:ff:ff:ff:ff
    inet 192.168.1.100/24 scope global vmbr0
       valid_lft forever preferred_lft forever
    inet6 fe80::264b:feff:fe52:7aa2/64 scope link
       valid_lft forever preferred_lft forever
8: vmbr1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
    link/ether 00:e0:4c:68:06:47 brd ff:ff:ff:ff:ff:ff
    inet 10.0.0.2/24 scope global vmbr1
       valid_lft forever preferred_lft forever
    inet6 fe80::2e0:4cff:fe68:647/64 scope link
       valid_lft forever preferred_lft forever

And these are the contents of the /etc/network/interfaces file
Code: 
auto lo
iface lo inet loopback

iface enp5s0 inet manual

iface enp10s0 inet manual

iface enp6s0 inet manual

iface enp7s0 inet manual

iface enp8s0 inet manual

auto vmbr0
iface vmbr0 inet static
        address 192.168.1.100/24
        gateway 192.168.1.1
        bridge-ports enp5s0
        bridge-stp off
        bridge-fd 0

auto vmbr1
iface vmbr1 inet static
        address 10.0.0.2/24
        bridge-ports enp9s0
        bridge-stp off
        bridge-fd 0

source /etc/network/interfaces.d/*
enp5s0 is the integrated gigabit nic on my motherboard (Asus Prime B550-Plus). I'm using it so I can access the web interface and have internet access on my pve host.


I'd be very grateful if someone could help me.
 
I got it working by disabling IOMMU in the bios (disabling it by kernel params didn't make the card work). I will eventually want to do pcie passthrough so when that comes up I'll have to factor in getting a less crappy network card... But for now I guess it'll be fine.
 
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