一些基本的诊断+配置：
$ cat /etc/lsb-release
DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=17.10
DISTRIB_CODENAME=artful
DISTRIB_DESCRIPTION="Ubuntu 17.10"
$ uname -a
Linux myhost 4.13.0-32-generic #35-Ubuntu SMP Thu Jan 25 09:13:46 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux
$ lspci
00:19.0 Ethernet controller: Intel Corporation 82577LM Gigabit Network Connection (rev 06)
$ dmesg
[ 2.044198] e1000e 0000:00:19.0 eth0: (PCI Express:2.5GT/s:Width x1) 00:26:2d:f2:a2:0c
[ 2.044200] e1000e 0000:00:19.0 eth0: Intel(R) PRO/1000 Network Connection
[ 2.044318] e1000e 0000:00:19.0 eth0: MAC: 9, PHY: 10, PBA No: A002FF-0FF
[ 2.045476] e1000e 0000:00:19.0 enp0s25: renamed from eth0
[ 38.880455] IPv6: ADDRCONF(NETDEV_UP): enp0s25: link is not ready
[ 39.076311] IPv6: ADDRCONF(NETDEV_UP): enp0s25: link is not ready
$ cat /etc/NetworkManager/system-connections/enp0s25
[connection]
id=enp0s25
uuid=444edb78-3e4f-4e97-a4cd-bf6970ba67b8
type=ethernet
interface-name=enp0s25
permissions=
timestamp=1518274444
[ethernet]
auto-negotiate=true
mac-address=00:26:2D:F2:A2:0C
mac-address-blacklist=
[ipv4]
dns-priority=100
dns-search=
may-fail=false
method=auto
[ipv6]
addr-gen-mode=stable-privacy
dns-priority=100
dns-search=
ip6-privacy=0
method=auto
$ ethtool enp0s25
Settings for enp0s25:
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
Advertised link modes: 10baseT/Half 10baseT/Full
100baseT/Half 100baseT/Full
1000baseT/Full
Advertised pause frame use: No
Advertised auto-negotiation: Yes
Speed: Unknown!
Duplex: Unknown! (255)
Port: Twisted Pair
PHYAD: 1
Transceiver: internal
Auto-negotiation: on
MDI-X: Unknown (auto)
Supports Wake-on: pumbg
Wake-on: g
Current message level: 0x00000007 (7)
drv probe link
Link detected: no
由于这是我两天前使用的同一根电缆，我担心硬件本身已经损坏。此外，我通过观察电缆和交换机端口在另一台 PC 上正常工作，排除了电缆和交换机端口的问题。还有其他原因可能导致这种情况吗？