Both suggested checks failed. The problem is not EEE, not jumbo frames, and not 5Gbps. After a link partner disappears, both r8169 ports come back with link up, but the data path stays dead until the NAS is rebooted.TMjack wrote: ↑03 Oct 2026, 08:18 Please perform the following verifications:
1. MTU verification: Change the MTU from 8192 to 1500 to determine whether the issue is related to Jumbo Frame configuration;
2. Link speed verification: Confirm whether the issue occurs only at 5Gbps, and test whether the same problem reproduces at 2500Mbps and 1000Mbps.
Tested on F2-425 Plus, TOS 7.0.1278, Intel N95.
eth0: 192.168.1.100/24 to the router, MAC 6c:bf:b5:05:4d:26
eth1: 10.10.10.1/24 direct to a Mac mini M4 via a bus-powered Thunderbolt 5GbE adapter, MAC 6c:bf:b5:05:4d:27
1. EEE off did not fix it.
ethtool --set-eee eth1 eee off was still disabled the next morning. After the Mac was powered off overnight, ping 10.10.10.1 failed with 100% loss. ethtool showed Speed 5000Mb/s, Duplex Full, Link detected yes. arping from eth1 got 0 responses. dmesg only had "Link is Down" and later "Link is Up - 5Gbps/Full", with no MAC/PHY error.
2. MTU 1500 did not fix it.
Both sides were set to MTU 1500, EEE still disabled. The next morning ping 10.10.10.1 failed again. eth1 was still mtu 1500, EEE disabled, link up at 5000Mb/s.
3. 1000Mbps did not fix it.
eth1 was forced to 1000Mbps full duplex on both sides, EEE still disabled. The next morning:
Code: Select all
ifconfig en10
media: 1000baseT <full-duplex>
4. eth0 fails the same way after a short link down.
The router reboots on a schedule every Tuesday at 03:00. After that reboot the router port still showed link up at 5000Mbps full duplex, but the NAS was not seen as a client: active no, rx/tx 0 bytes, no new DHCP request from 6c:bf:b5:05:4d:26. 192.168.1.100 did not answer.
This morning both paths were dead at the same time, so SSH was impossible and ip link down/up could not be run. Only a NAS reboot recovered both ports. After reboot eth0 and eth1 are up at 5000Mbps full, and ping works on 10.10.10.1 and 192.168.1.1.
Please check the r8169 MAC re-init on link-up for both 0000:02:00.0 eth0 and 0000:03:00.0 eth1. The PHY reports link up, but the port does not pass traffic until the interface is reopened or the NAS is rebooted.




