Hello, I noticed that wired Ethernet throughput from WAN is much lower than expected on my new ThinkPad P14s Gen6 Intel. The culprit seems to be CRC errors. This is with current firmware. I updated everything one or two weeks ago. Executing ‘ethtool --set-priv-flags enp0s31f6 disable-k1 on’ works around the problem. There could be a relation to commit 578294b8b60d that re-enabled K1 by default. See below for a shell session demonstrating the problem by downloading data for 30 seconds. With K1 enabled, the transfer generated 125 CRC errors while receiving 156 MiB; with K1 disabled, the error counter remained unchanged while receiving 2547 MiB (i.e. a 16-fold faster download). The following has been recorded using a freshly booted current Debian testing live system. I’ve been observing the same problem with different recent kernel versions, different network cables, routers, and networks. I also had the opportunity to reproduce the problem with a second identical computer. Cheers Christoph ---------------------------------------------------------------- root@debian:~# uname -a Linux debian 7.2.6+deb14-amd64 #1 SMP PREEMPT_DYNAMIC Debian 7.2.6-1 (2026-09-16) x86_64 GNU/Linux root@debian:~# ethtool --show-priv-flags enp0s31f6 Private flags for enp0s31f6: s0ix-enabled: on disable-k1 : off root@debian:~# ip -s -s link show dev enp0s31f6 2: enp0s31f6: mtu 1500 qdisc fq_codel state UP mode DEFAULT group default qlen 1000 link/ether [hidden] brd ff:ff:ff:ff:ff:ff RX: bytes packets errors dropped missed mcast 26981 189 0 0 0 72 RX errors: length crc frame fifo overrun 0 0 0 0 0 TX: bytes packets errors dropped carrier collsns 10442 89 0 0 0 0 TX errors: aborted fifo window heartbt transns 0 0 0 0 2 altname enx[hidden] root@debian:~# curl --max-time 30 -o /dev/null http://test-debit.free.fr/10485760.rnd % Total % Received % Xferd Average Speed Time Time Time Current Dload Upload Total Spent Left Speed 1 10.00G 1 153.9M 0 0 5.28M 0 32:18 00:29 31:49 5.58M curl: (28) Operation timed out after 30000 milliseconds with 163226929 out of 10737418240 bytes received root@debian:~# ip -s -s link show dev enp0s31f6 2: enp0s31f6: mtu 1500 qdisc fq_codel state UP mode DEFAULT group default qlen 1000 link/ether [hidden] brd ff:ff:ff:ff:ff:ff RX: bytes packets errors dropped missed mcast 171179576 112998 250 0 0 96 RX errors: length crc frame fifo overrun 0 125 0 0 0 TX: bytes packets errors dropped carrier collsns 1102954 15430 0 0 0 0 TX errors: aborted fifo window heartbt transns 0 0 0 0 2 altname enx[hidden] root@debian:~# ethtool --set-priv-flags enp0s31f6 disable-k1 on root@debian:~# ethtool --show-priv-flags enp0s31f6 Private flags for enp0s31f6: s0ix-enabled: on disable-k1 : on root@debian:~# curl --max-time 30 -o /dev/null http://test-debit.free.fr/10485760.rnd % Total % Received % Xferd Average Speed Time Time Time Current Dload Upload Total Spent Left Speed 23 10.00G 23 2.38G 0 0 84.23M 0 02:01 00:29 01:32 104.7M curl: (28) Operation timed out after 30000 milliseconds with 2670737217 out of 10737418240 bytes received root@debian:~# ip -s -s link show dev enp0s31f6 2: enp0s31f6: mtu 1500 qdisc fq_codel state UP mode DEFAULT group default qlen 1000 link/ether [hidden] brd ff:ff:ff:ff:ff:ff RX: bytes packets errors dropped missed mcast 2972820757 1958686 250 0 0 122 RX errors: length crc frame fifo overrun 0 125 0 0 0 TX: bytes packets errors dropped carrier collsns 13144890 187359 0 0 0 0 TX errors: aborted fifo window heartbt transns 0 0 0 0 4 altname enx[hidden] ---------------------------------------------------------------- Information from /sys/class/dmi/id/: sys_vendor: LENOVO product_name: 21QTS28200 product_version: ThinkPad P14s Gen 6 board_name: 21QTS28200 bios_vendor: LENOVO bios_version: R2WET44W (1.26 ) bios_date: 06/30/2026 Information about the Ethernet adapter: # lspci -nnvv -s 00:1f.6 00:1f.6 Ethernet controller [0200]: Intel Corporation Ethernet Connection (24) I219-V [8086:57a1] Subsystem: Lenovo Device [17aa:512b] Control: I/O- Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx+ Status: Cap+ 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort- SERR-