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Since a few days I am experiencing a flapping Ethernet connection on my Fedora 23 laptop: the network connection goes down for several seconds every minute.

The machine is up-to-date with the latest kernel (4.4.6) and packages.

UPDATE: The problem persists in different environments (different cables and switches) and regardless of static or DHCP addressing; the connection with an USB-Eth adapter worked for one hour or so, then started behaving the same way. Booting on an older kernel (4.4.3) did not solve the problem. However, when booting on a Live CD with Fedora 21, the wired network seems to work.

Anyone has experienced this issue? Here's some troubleshooting output (concerning the eth device enp0s25):

[root@linuxbox ~]# ip address
(...)
2: enp0s25: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
    link/ether ec:b1:d7:97:9d:f2 brd ff:ff:ff:ff:ff:ff
    inet 10.10.10.13/24 brd 10.10.10.255 scope global enp0s25
       valid_lft forever preferred_lft forever
    inet6 fe80::eeb1:d7ff:fe97:9df2/64 scope link 
       valid_lft forever preferred_lft forever
(...)


[root@linuxbox ~]# dmesg 
(...) 
[ 1403.944457] ax88179_178a 4-5:1.0 enp0s20u5: ax88179 - Link status is: 0
[ 1409.490222] e1000e: enp0s25 NIC Link is Up 100 Mbps Full Duplex, Flow Control: None
[ 1409.490232] e1000e 0000:00:19.0 enp0s25: 10/100 speed: disabling TSO


[root@linuxbox ~]# ping www.google.com
PING www.google.com (172.217.16.132) 56(84) bytes of data.
64 bytes from zrh04s06-in-f4.1e100.net (172.217.16.132): icmp_seq=1 ttl=54 time=4.79 ms
64 bytes from zrh04s06-in-f4.1e100.net (172.217.16.132): icmp_seq=2 ttl=54 time=4.48 ms
64 bytes from zrh04s06-in-f4.1e100.net (172.217.16.132): icmp_seq=3 ttl=54 time=4.57 ms
64 bytes from zrh04s06-in-f4.1e100.net (172.217.16.132): icmp_seq=50 ttl=54 time=4.62 ms
64 bytes from zrh04s06-in-f4.1e100.net (172.217.16.132): icmp_seq=51 ttl=54 time=4.50 ms
64 bytes from zrh04s06-in-f4.1e100.net (172.217.16.132): icmp_seq=52 ttl=54 time=4.81 ms
64 bytes from zrh04s06-in-f4.1e100.net (172.217.16.132): icmp_seq=53 ttl=54 time=6.16 ms
(...)
^C
--- www.google.com ping statistics ---
65 packets transmitted, 11 received, 83% packet loss, time 64018ms
rtt min/avg/max/mdev = 4.486/4.803/6.164/0.469 ms


[root@linuxbox ~]# 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: 100Mb/s
    Duplex: Full
    Port: Twisted Pair
    PHYAD: 1
    Transceiver: internal
    Auto-negotiation: on
    MDI-X: off (auto)
    Supports Wake-on: pumbg
    Wake-on: g
    Current message level: 0x00000007 (7)
                   drv probe link
    Link detected: yes


[root@linuxbox ~]# ethtool -S enp0s25
NIC statistics:
     rx_packets: 10222
     tx_packets: 1774
     rx_bytes: 1146761
     tx_bytes: 250438
     rx_broadcast: 9287
     tx_broadcast: 37
     rx_multicast: 84
     tx_multicast: 102
     rx_errors: 0
     tx_errors: 0
     tx_dropped: 0
     multicast: 84
     collisions: 0
     rx_length_errors: 0
     rx_over_errors: 0
     rx_crc_errors: 0
     rx_frame_errors: 0
     rx_no_buffer_count: 0
     rx_missed_errors: 0
     tx_aborted_errors: 0
     tx_carrier_errors: 0
     tx_fifo_errors: 0
     tx_heartbeat_errors: 0
     tx_window_errors: 0
     tx_abort_late_coll: 0
     tx_deferred_ok: 0
     tx_single_coll_ok: 0
     tx_multi_coll_ok: 0
     tx_timeout_count: 0
     tx_restart_queue: 0
     rx_long_length_errors: 0
     rx_short_length_errors: 0
     rx_align_errors: 0
     tx_tcp_seg_good: 0
     tx_tcp_seg_failed: 0
     rx_flow_control_xon: 0
     rx_flow_control_xoff: 0
     tx_flow_control_xon: 0
     tx_flow_control_xoff: 0
     rx_csum_offload_good: 9429
     rx_csum_offload_errors: 0
     rx_header_split: 0
     alloc_rx_buff_failed: 0
     tx_smbus: 0
     rx_smbus: 0
     dropped_smbus: 0
     rx_dma_failed: 0
     tx_dma_failed: 0
     rx_hwtstamp_cleared: 0
     uncorr_ecc_errors: 0
     corr_ecc_errors: 0
     tx_hwtstamp_timeouts: 0


[root@linuxbox ~]# uname -a
Linux linuxbox 4.4.6-300.fc23.x86_64 #1 SMP Wed Mar 16 22:10:37 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux


[root@linuxbox ~]# lspci
00:00.0 Host bridge: Intel Corporation Xeon E3-1200 v3/4th Gen Core Processor DRAM Controller (rev 06)
00:02.0 VGA compatible controller: Intel Corporation 4th Gen Core Processor Integrated Graphics Controller (rev 06)
00:03.0 Audio device: Intel Corporation Xeon E3-1200 v3/4th Gen Core Processor HD Audio Controller (rev 06)
00:14.0 USB controller: Intel Corporation 8 Series/C220 Series Chipset Family USB xHCI (rev 04)
00:16.0 Communication controller: Intel Corporation 8 Series/C220 Series Chipset Family MEI Controller #1 (rev 04)
00:19.0 Ethernet controller: Intel Corporation Ethernet Connection I217-V (rev 04)
00:1a.0 USB controller: Intel Corporation 8 Series/C220 Series Chipset Family USB EHCI #2 (rev 04)
00:1b.0 Audio device: Intel Corporation 8 Series/C220 Series Chipset High Definition Audio Controller (rev 04)
00:1c.0 PCI bridge: Intel Corporation 8 Series/C220 Series Chipset Family PCI Express Root Port #1 (rev d4)
00:1c.6 PCI bridge: Intel Corporation 8 Series/C220 Series Chipset Family PCI Express Root Port #7 (rev d4)
00:1c.7 PCI bridge: Intel Corporation 8 Series/C220 Series Chipset Family PCI Express Root Port #8 (rev d4)
00:1d.0 USB controller: Intel Corporation 8 Series/C220 Series Chipset Family USB EHCI #1 (rev 04)
00:1f.0 ISA bridge: Intel Corporation HM87 Express LPC Controller (rev 04)
00:1f.2 SATA controller: Intel Corporation 8 Series/C220 Series Chipset Family 6-port SATA Controller 1 [AHCI mode] (rev 04)
00:1f.3 SMBus: Intel Corporation 8 Series/C220 Series Chipset Family SMBus Controller (rev 04)
02:00.0 Network controller: Broadcom Corporation BCM43228 802.11a/b/g/n
03:00.0 Unassigned class [ff00]: Realtek Semiconductor Co., Ltd. RTS5227 PCI Express Card Reader (rev 01)

Related question.

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I think the problem is solved in one environment. Apparently someone else set his IP address (statically) the same as mine (static too). The conflict of IP addresses caused this behaviour.

The problem presents itself also in another environment where everybody uses (or is supposed to use) DHCP addressing. I'll check this and update this answer if I find out that this was the cause of the problem.

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