BPI R4 PRO 10G RJ45 WAN/LAN link @1Gb flapping problem

rbtree · December 25, 2025, 6:49pm

I have an issue with both 10G RJ45 WAN & 10G RJ45 LAN ports, when connected to a 1G partner.

The link functions correctly under high rx achieving ~995Mbit/s using iperf3 (both udp and tcp), but in the other direction with tx > ~100Mbit/s, the interface goes down, 100% reproducible.

I’ve tested this with both a dell precision 7680 laptop (Intel i219LM) & cisco EPC3940L cable modem. the BPI R4 PRO is running the image it came with:

BUILD_ID="unknown"
OPENWRT_RELEASE="OpenWrt 24.10-SNAPSHOT unknown"
OPENWRT_BUILD_DATE="1750129753"

The issue does not reproduce with the 2.5G lan port or 1G lan port (which i’ve now repurposed for uplink), so i think the ethernet cables i tested with can be ruled out as cause.

Logs:

Dec 24 00:38:57 10.222.1.2 netifd: Network device 'eth1' link is up
Dec 24 00:38:57 10.222.1.2 kernel: [256130.672313] mtk_soc_eth 15100000.ethernet eth1: Link is Up - 1Gbps/Full - flow control rx/tx
...
Dec 24 00:40:36 10.222.1.2 kernel: [256229.115052] mtk_soc_eth 15100000.ethernet eth1: Link is Down
Dec 24 00:40:36 10.222.1.2 netifd: Network device 'eth1' link is down

Dec 24 04:30:51 10.222.1.2 kernel: [270044.316592] mxl862xx mdio-bus:10 mxl_lan5: Link is Up - 1Gbps/Full - flow control rx/tx
Dec 24 04:30:51 10.222.1.2 kernel: [270044.316612] br-lan: port 6(mxl_lan5) entered blocking state
Dec 24 04:30:51 10.222.1.2 kernel: [270044.330348] br-lan: port 6(mxl_lan5) entered forwarding state
...
Dec 24 04:44:24 10.222.1.2 netifd: Network device 'mxl_lan5' link is down
Dec 24 04:44:24 10.222.1.2 kernel: [270857.132131] mxl862xx mdio-bus:10 mxl_lan5: Link is Down
Dec 24 04:44:24 10.222.1.2 kernel: [270857.138601] br-lan: port 6(mxl_lan5) entered disabled state

Is this a known issue?

Any workarounds or next troubleshooting steps that can be recommended?

newAM · December 26, 2025, 2:11am

I am not sure if this is helpful; I also observed link flapping with the BPi-R4 (non-pro), however unlike your issue this was only observed at peak loads, >=1Gbps RX from WAN to LAN. This is reproducible, but not with synthetic loads such as iperf.

Dec 15 18:39:30 bpi kernel: mtk_soc_eth 15100000.ethernet end0: Link is Down
Dec 15 18:39:30 bpi kernel: mtk_soc_eth 15100000.ethernet: warm reset failed
Dec 15 18:39:30 bpi kernel: mtk_soc_eth 15100000.ethernet end0: configuring for fixed/internal link mode
Dec 15 18:39:30 bpi kernel: mtk_soc_eth 15100000.ethernet end0: Link is Up - 10Gbps/Full - flow control rx/tx
Dec 15 18:40:20 bpi kernel: mtk_soc_eth 15100000.ethernet end0: Link is Down
Dec 15 18:40:20 bpi kernel: mtk_soc_eth 15100000.ethernet: warm reset failed
Dec 15 18:40:20 bpi kernel: mtk_soc_eth 15100000.ethernet end0: configuring for fixed/internal link mode
Dec 15 18:40:20 bpi kernel: mtk_soc_eth 15100000.ethernet end0: Link is Up - 10Gbps/Full - flow control rx/tx
Dec 15 18:40:45 bpi kernel: mtk_soc_eth 15100000.ethernet end0: Link is Down
Dec 15 18:40:45 bpi kernel: mtk_soc_eth 15100000.ethernet: warm reset failed
Dec 15 18:40:45 bpi kernel: mtk_soc_eth 15100000.ethernet end0: configuring for fixed/internal link mode
Dec 15 18:40:45 bpi kernel: mtk_soc_eth 15100000.ethernet end0: Link is Up - 10Gbps/Full - flow control rx/tx

This was with Frank-W’s kernel ontop of my own custom NixOS install: Linux bpi 6.12.61-bpi-r4 #1-NixOS SMP Tue Jan 1 00:00:00 UTC 1980 aarch64 GNU/Linux

I observed this for the first time with 6.12.61, and I have been using this router in production for over a year before that without issue.

What kernel version does OpenWrt 24.10 have?

rbtree · December 26, 2025, 2:52am

What kernel version does OpenWrt 24.10 have?

Linux x 6.6.93 #0 SMP Tue Jun 17 03:09:13 2025 aarch64 GNU/Linux

frank-w · December 26, 2025, 8:25am

Have you tested if this happens also if only one interface involved (no routing) or with ppe disabled?

rbtree · January 1, 2026, 7:25pm

my initial test above was with no routing, to narrow down the issue. iperf3 running on the BPI R4 directly.

is the PPE relevant in that case?

frank-w · January 1, 2026, 8:48pm

No ppe is for routing acceleration. I ask because in the other thread there is routed traffic, no issue on direct traffic to R4…so a bit different.

Any hints in dmesg? Have you looked on temperatures? I did not make much loadtests because i have no heatsink yet and only fan standing next to the board sometimes.

rbtree · January 4, 2026, 10:02pm

found some time to conduct a new test, this time with console & dmesg logs

test setup:

bpi r4 pro, eth1 1.1.1.1 removed from bridge, connected directly to dell laptop mentioned above with 1Gb RJ45 interface 1.1.1.2, cat7 cable, link negotiates @ 1Gb/s

test report, see attachment for full result:

bpi.r4.pro.link.flaps.testing.txt (29.5 KB)

dell side → paste.sh · encrypted pastebin

1 - eth1 flow control off

1.1 bpi `eth1` → dell, udp @ attempt 2000Mbit/s, effective 1Gbit/s 30sec:

root@banana:~# iperf3 -c 1.1.1.2 -u -b 2000M -t 30

no link flaps, bitrate ~955Mb/s

[ ID] Interval           Transfer     Bitrate         Jitter    Lost/Total Datagrams
[  5]   0.00-30.00  sec  3.34 GBytes   956 Mbits/sec  0.000 ms  0/2476966 (0%)  sender
[  5]   0.00-30.00  sec  3.34 GBytes   956 Mbits/sec  0.011 ms  1060/2476948 (0.043%)  receiver

1.2 bpi `eth1` → dell, tcp @ attempt 2000Mbit/s, effective 1Gbit/s, 30sec:

root@banana:~# iperf3 -c 1.1.1.2 -b 2000M -t 30

2 link flaps, bitrate is abysmal

[1287663.678450] mtk_soc_eth 15100000.ethernet eth1: Link is Down
[1287666.831919] mtk_soc_eth 15100000.ethernet eth1: Link is Up - 1Gbps/Full - flow control off
[1287677.198451] mtk_soc_eth 15100000.ethernet eth1: Link is Down
[1287680.351918] mtk_soc_eth 15100000.ethernet eth1: Link is Up - 1Gbps/Full - flow control off

[ ID] Interval           Transfer     Bitrate         Retr
[  5]   0.00-30.00  sec  2.12 MBytes   594 Kbits/sec  312             sender
[  5]   0.00-33.48  sec  2.12 MBytes   532 Kbits/sec                  receiver

2 - eth1 flow control ON

2.1 bpi `eth1` → dell, udp @ attempt 2000Mbit/s, effective 1Gbit/s, 30sec:

root@banana:~# iperf3 -c 1.1.1.2 -u -b 2000M -t 30

no link flaps, bitrate ~955Mb/s

[ ID] Interval           Transfer     Bitrate         Jitter    Lost/Total Datagrams
[  5]   0.00-30.00  sec  3.34 GBytes   956 Mbits/sec  0.000 ms  0/2476949 (0%)  sender
[  5]   0.00-30.00  sec  3.34 GBytes   956 Mbits/sec  0.016 ms  781/2476923 (0.032%)  receiver

2.1 bpi `eth1` → dell, tcp @ attempt 2000Mbit/s, effective 1Gbit/s, 30sec:

root@banana:~# iperf3 -c 1.1.1.2 -b 2000M -t 30

2 link flaps, bitrate is abysmal

[1288412.718445] mtk_soc_eth 15100000.ethernet eth1: Link is Down
[1288415.871926] mtk_soc_eth 15100000.ethernet eth1: Link is Up - 1Gbps/Full - flow control rx/tx
[1288427.278445] mtk_soc_eth 15100000.ethernet eth1: Link is Down
[1288430.441911] mtk_soc_eth 15100000.ethernet eth1: Link is Up - 1Gbps/Full - flow control rx/tx

[ ID] Interval           Transfer     Bitrate         Retr
[  5]   0.00-30.00  sec  1.12 MBytes   315 Kbits/sec  323             sender
[  5]   0.00-30.89  sec  1.00 MBytes   272 Kbits/sec                  receiver

3 - eth1 flow control ON, reverse direction traffic

3.1 bpi `eth1` ← dell, udp @ 2000Mbit/s, 30sec:

root@banana:~# iperf3 -s
C:\>iperf3 -c 1.1.1.1 -b 2G -u -t 30

no link flaps, bitrate ~945Mb/s

[ ID] Interval           Transfer     Bitrate         Jitter    Lost/Total Datagrams
[  5]   0.00-30.01  sec  3.30 GBytes   945 Mbits/sec  0.016 ms  329/2428771 (0.014%)  receiver

3.2 bpi `eth1` ← dell, tcp @ 2000Mbit/s, 30sec:

C:\>iperf3 -c 1.1.1.1 -b 2G -t 30

no link flaps, bitrate 942Mb/s

[ ID] Interval           Transfer     Bitrate
[  5]   0.00-30.05  sec  3.29 GBytes   942 Mbits/sec                  receiver

temperatures:

frank-w · January 4, 2026, 11:14pm

So basicly tcp to dell independ of flow control…or did you have it configured only on one side?..only wondering about 2000mbit/s. You and log say 1gbit/s.

rbtree · January 4, 2026, 11:28pm

or did you have it configured only on one side?

dell side is windows default settings, flow control is auto negotiation. except from full log:

root@banana:~# ip l s eth1 down                                                                                                                       
root@banana:~# ethtool -s eth1 autoneg on
root@banana:~# ethtool -A eth1 autoneg on                                                                                                             


[1288230.751911] mtk_soc_eth 15100000.ethernet eth1: Link is Up - 1Gbps/Full - flow control rx/tx

root@banana:~# ethtool eth1
Settings for eth1:
        Supported ports: [ TP    MII ]
        Supported link modes:   100baseT/Full
                                1000baseT/Half 1000baseT/Full
                                10000baseT/Full
                                2500baseT/Full
                                5000baseT/Full
        Supported pause frame use: Symmetric Receive-only
        Supports auto-negotiation: Yes
        Supported FEC modes: Not reported
        Advertised link modes:  100baseT/Full
                                1000baseT/Half 1000baseT/Full
                                10000baseT/Full
                                2500baseT/Full
                                5000baseT/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
        Port: Twisted Pair
        PHYAD: 1c
        Transceiver: external
        MDI-X: Unknown
        Current message level: 0x000000ff (255)
                               drv probe link timer ifdown ifup rx_err tx_err
        Link detected: yes
root@banana:~#

only wondering about 2000mbit/s. You and log say 1gbit/s.

2000Mbit/s is what iperf3 attempts, i’ve now edited the post for clarity

rbtree · January 4, 2026, 11:47pm

tried

root@banana:~# ethtool -K eth1 tso off gso off

otherwise same setup as above.

root@banana:~# 
root@banana:~# ethtool -k eth1  | grep -v fixed
Features for eth1:
rx-checksumming: on
tx-checksumming: on
        tx-checksum-ipv4: on
        tx-checksum-ipv6: on
scatter-gather: on
        tx-scatter-gather: on
tcp-segmentation-offload: off
        tx-tcp-segmentation: off
        tx-tcp-ecn-segmentation: off
        tx-tcp-mangleid-segmentation: off
        tx-tcp6-segmentation: off
generic-segmentation-offload: off
generic-receive-offload: on
large-receive-offload: off
tx-vlan-offload: on
tx-nocache-copy: off
hw-tc-offload: on
rx-gro-list: off
rx-udp-gro-forwarding: off
root@banana:~#

does not reproduce anymore

root@banana:~# iperf3 -c 1.1.1.2 -b 2000M -t 30
Connecting to host 1.1.1.2, port 5201
[  5] local 1.1.1.1 port 39740 connected to 1.1.1.2 port 5201
[ ID] Interval           Transfer     Bitrate         Retr  Cwnd
[  5]   0.00-1.00   sec   114 MBytes   958 Mbits/sec    0    383 KBytes       
[  5]   1.00-2.00   sec   112 MBytes   938 Mbits/sec    0    402 KBytes       
[  5]   2.00-3.00   sec   112 MBytes   941 Mbits/sec    0    402 KBytes       
[  5]   3.00-4.00   sec   112 MBytes   938 Mbits/sec    6    310 KBytes       
[  5]   4.00-5.00   sec   112 MBytes   935 Mbits/sec    0    361 KBytes       
[  5]   5.00-6.00   sec   113 MBytes   948 Mbits/sec    0    387 KBytes       
[  5]   6.00-7.00   sec   112 MBytes   940 Mbits/sec    0    387 KBytes       
[  5]   7.00-8.00   sec   113 MBytes   945 Mbits/sec    0    489 KBytes       
[  5]   8.00-9.00   sec   112 MBytes   940 Mbits/sec    0    489 KBytes       
[  5]   9.00-10.00  sec   113 MBytes   945 Mbits/sec    0    489 KBytes       
[  5]  10.00-11.00  sec   112 MBytes   936 Mbits/sec    0    489 KBytes       
[  5]  11.00-12.00  sec   112 MBytes   944 Mbits/sec    0    489 KBytes       
[  5]  12.00-13.00  sec   112 MBytes   941 Mbits/sec   84    395 KBytes       
[  5]  13.00-14.00  sec   112 MBytes   935 Mbits/sec    0    484 KBytes       
[  5]  14.00-15.00  sec   113 MBytes   949 Mbits/sec    0    484 KBytes       
[  5]  15.00-16.00  sec   112 MBytes   936 Mbits/sec    0    484 KBytes       
[  5]  16.00-17.00  sec   112 MBytes   942 Mbits/sec    0    491 KBytes       
[  5]  17.00-18.00  sec   112 MBytes   944 Mbits/sec    0    491 KBytes       
[  5]  18.00-19.00  sec   111 MBytes   933 Mbits/sec   59    362 KBytes       
[  5]  19.00-20.00  sec   112 MBytes   941 Mbits/sec    0    403 KBytes       
[  5]  20.00-21.00  sec   113 MBytes   947 Mbits/sec    0    462 KBytes       
[  5]  21.00-22.00  sec   112 MBytes   936 Mbits/sec    0    462 KBytes       
[  5]  22.00-23.00  sec   113 MBytes   946 Mbits/sec    0    462 KBytes       
[  5]  23.00-24.00  sec   111 MBytes   931 Mbits/sec   40    366 KBytes       
[  5]  24.00-25.00  sec   113 MBytes   948 Mbits/sec    0    403 KBytes       
[  5]  25.00-26.00  sec   112 MBytes   935 Mbits/sec    0    403 KBytes       
[  5]  26.00-27.00  sec   113 MBytes   945 Mbits/sec    0    409 KBytes       
[  5]  27.00-28.00  sec   112 MBytes   937 Mbits/sec    0    409 KBytes       
[  5]  28.00-29.00  sec   112 MBytes   944 Mbits/sec    0    414 KBytes       
[  5]  29.00-30.00  sec   112 MBytes   941 Mbits/sec    0    414 KBytes       
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bitrate         Retr
[  5]   0.00-30.00  sec  3.29 GBytes   941 Mbits/sec  189             sender
[  5]   0.00-30.00  sec  3.29 GBytes   941 Mbits/sec                  receiver

iperf Done.
root@banana:~#

which driver or chip has a bug?

cc @sinovoip

frank-w · January 10, 2026, 4:51pm

maybe you could try this?

https://git01.mediatek.com/plugins/gitiles/openwrt/feeds/mtk-openwrt-feeds/+/a06a45e218bd84ac87a8eaae4815d56056f7dad5

rbtree · January 11, 2026, 8:22pm

any hints on top of what i could apply that on, to retain current functionality of bpi shipped image?

frank-w · January 11, 2026, 8:30pm

You have to rebuild image from code after applying this patch…either bpi image or just openwrt with mtk feeds

rbtree · January 11, 2026, 9:10pm

following refs/heads/master - openwrt/feeds/mtk-openwrt-feeds - Gitiles

there is no target profile for BPI-R4-PRO:

frank-w · January 11, 2026, 9:14pm

Afair there was a special doing for R4Pro, could be different now.

https://wiki.fw-web.de/doku.php?id=en:bpi-r4pro:start#openwrt

not sure if you can add the patch there

Alao you can try my debian and kernel, and change to usxgmii…afair i had tried it,but currently it is base-r

BPI R4 PRO 10G RJ45 WAN/LAN link @1Gb flapping problem

1 - eth1 flow control off

1.1 bpi eth1 → dell, udp @ attempt 2000Mbit/s, effective 1Gbit/s 30sec:

1.2 bpi eth1 → dell, tcp @ attempt 2000Mbit/s, effective 1Gbit/s, 30sec:

2 - eth1 flow control ON

2.1 bpi eth1 → dell, udp @ attempt 2000Mbit/s, effective 1Gbit/s, 30sec:

2.1 bpi eth1 → dell, tcp @ attempt 2000Mbit/s, effective 1Gbit/s, 30sec: