I have a Buffalo WZR-HP-AG300H that I use as AP. After updating it to 21.02.0, the uplink port eth1 that is connected to a switch is negotiating at 100 Mb/s.
I'm sure that before the upgrade this link was working at 1000Mb/s. I've tested the cable and is perfectly fine and if I force the 1000 Mb speed in the switch the link is marked as down. Also 1000BaseT is no longer advertised as a supported mode in ethtool.
I've already workarounded the issue using an unused port in the internal switch, but it'd be nice if it can be fixed.
# ethtool eth1 Settings for eth1: Supported ports: [ TP MII ] Supported link modes: 10baseT/Half 10baseT/Full 100baseT/Half 100baseT/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 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 Link partner advertised pause frame use: No Link partner advertised auto-negotiation: Yes Link partner advertised FEC modes: Not reported Speed: 100Mb/s Duplex: Full Port: MII PHYAD: 4 Transceiver: external Auto-negotiation: on Current message level: 0x000000ff (255) drv probe link timer ifdown ifup rx_err tx_err Link detected: yes # dmesg | grep eth1 [ 2.579283] eth1: Atheros AG71xx at 0xba000000, irq 5, mode: rgmii [ 76.682973] eth1: link up (100Mbps/Full duplex) # uname -a Linux gluon 5.4.143 #0 Tue Aug 31 22:20:08 2021 mips GNU/Linux