
これに似た問題がすでに解決されているようです。ケーブルを交換することで解決しました。私も同じ問題を抱えていますが、ハードウェアの問題ではないと思われます。私の sudo lshw -C ネットワークは次のとおりです。
*-network
description: Ethernet interface
product: RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller
vendor: Realtek Semiconductor Co., Ltd.
physical id: 0
bus info: pci@0000:07:00.0
logical name: enp7s0
version: 07
serial: b8:ca:3a:ca:44:6d
size: 100Mbit/s
capacity: 1Gbit/s
width: 64 bits
clock: 33MHz
capabilities: pm msi pciexpress msix vpd bus_master cap_list ethernet physical tp 10bt 10bt-fd 100bt 100bt-fd 1000bt-fd autonegotiation
configuration: autonegotiation=on broadcast=yes driver=r8168 driverversion=8.045.08-NAPI duplex=full ip=192.168.1.128 latency=0 link=yes multicast=yes port=twisted pair speed=100Mbit/s
resources: irq:27 ioport:2000(size=256) memory:d1404000-d1404fff memory:d1400000-d1403fff
sudo ethtool enp7s0 は次のとおりです:
Settings for enp7s0:
Supported ports: [ TP ]
Supported link modes: 10baseT/Half 10baseT/Full
100baseT/Half 100baseT/Full
1000baseT/Full
Supported pause frame use: No
Supports auto-negotiation: Yes
Supported FEC modes: Not reported
Advertised link modes: 10baseT/Half 10baseT/Full
100baseT/Half 100baseT/Full
1000baseT/Full
Advertised pause frame use: No
Advertised auto-negotiation: Yes
Advertised FEC modes: Not reported
Speed: 100Mb/s
Duplex: Full
Port: Twisted Pair
PHYAD: 0
Transceiver: internal
Auto-negotiation: on
MDI-X: Unknown
Supports Wake-on: pumbg
Wake-on: g
Current message level: 0x00000033 (51)
drv probe ifdown ifup
Link detected: yes
これはハードウェアの問題ではないとしか思えません。なぜなら、最近これを実行したことがあったからです (Ubuntu 18.04.2 LTS を実行している同じラップトップ、同じルーター、同じケーブル)。これは sudo ethtool enps70 でした:
Settings for enp7s0:
Supported ports: [ TP ]
Supported link modes: 10baseT/Half 10baseT/Full
100baseT/Half 100baseT/Full
1000baseT/Full
Supported pause frame use: No
Supports auto-negotiation: Yes
Supported FEC modes: Not reported
Advertised link modes: 10baseT/Half 10baseT/Full
100baseT/Half 100baseT/Full
1000baseT/Full
Advertised pause frame use: No
Advertised auto-negotiation: Yes
Advertised FEC modes: Not reported
Speed: 1000Mb/s
Duplex: Full
Port: Twisted Pair
PHYAD: 0
Transceiver: internal
Auto-negotiation: on
MDI-X: Unknown
Supports Wake-on: pumbg
Wake-on: g
Current message level: 0x00000033 (51)
drv probe ifdown ifup
Link detected: yes
しかし、今は速度を1000に設定できません