I have two gigabit devices connected to a gigabit switch using cat 5e ethernet cables, but the wirings on the RJ45 connectors do not respect any of the established color standards, because they were made by a newcomer.
The connection between the devices is working, but only at 100Mb/s speed. When I check the NIC details using ethtool, the devices properly show up as gigabit capable.
Settings for eth0:
Supported ports: [ TP ]
Supported link modes: 10baseT/Half 10baseT/Full
100baseT/Half 100baseT/Full
1000baseT/Full
Supported pause frame use: Symmetric
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: Symmetric
Advertised auto-negotiation: Yes
Advertised FEC modes: Not reported
Speed: 100Mb/s
Duplex: Full
Port: Twisted Pair
PHYAD: 1
Transceiver: internal
Auto-negotiation: on
MDI-X: on (auto)
Supports Wake-on: pumbg
Wake-on: g
Current message level: 0x00000007 (7)
drv probe link
Link detected: yes
If I unplug and replug the cables, I see the Speed being initially set to 1Gb/s, but then after a couple of seconds being downgraded to 100Mb/s.
[1469117.206807] igb 0000:01:00.0 eth0: igb: eth0 NIC Link is Down
[1469117.206899] br0: port 2(eth0) entered disabled state
[1469121.997530] igb 0000:01:00.0 eth0: igb: eth0 NIC Link is Up 1000 Mbps Full Duplex, Flow Control: RX
[1469124.437297] igb 0000:01:00.0: exceed max 2 second
[1469124.437568] igb 0000:01:00.0 eth0: igb: eth0 NIC Link is Down
[1469125.877831] igb 0000:01:00.0 eth0: igb: eth0 NIC Link is Up 1000 Mbps Full Duplex, Flow Control: RX
[1469128.307603] igb 0000:01:00.0: exceed max 2 second
[1469128.307875] igb 0000:01:00.0 eth0: igb: eth0 NIC Link is Down
[1469129.748145] igb 0000:01:00.0 eth0: igb: eth0 NIC Link is Up 1000 Mbps Full Duplex, Flow Control: RX
[1469132.178032] igb 0000:01:00.0: exceed max 2 second
[1469132.178301] igb 0000:01:00.0 eth0: igb: eth0 NIC Link is Down
[1469132.558348] igb 0000:01:00.0 eth0: igb: eth0 NIC Link is Up 100 Mbps Full Duplex, Flow Control: RX
[1469132.558572] br0: port 2(eth0) entered blocking state
[1469132.558574] br0: port 2(eth0) entered forwarding state
The exact same problem is happening with identical wired cables and the same intel NICs, on other two devices connected to the very same switch.
# ip -d link show dev eth0
2: eth0: <BROADCAST,MULTICAST,PROMISC,UP,LOWER_UP> mtu 1500 qdisc mq master br0 state UP mode DEFAULT group default qlen 1000
link/ether XX:XX:XX:XX:XX:XX brd ff:ff:ff:ff:ff:ff promiscuity 2 minmtu 68 maxmtu 9216
bridge_slave state forwarding priority 32 cost 19 hairpin off guard off root_block off fastleave off learning on flood on port_id 0x8002 port_no 0x2 designated_port 32770 designated_cost 0 designated_bridge 0000.80:c6:ca:1:56:4e designated_root 0000.80:c6:ca:1:56:4e hold_timer 0.00 message_age_timer 0.00 forward_delay_timer 0.00 topology_change_ack 0 config_pending 0 proxy_arp off proxy_arp_wifi off mcast_router 1 mcast_fast_leave off mcast_flood on neigh_suppress off group_fwd_mask 0x0 group_fwd_mask_str 0x0 vlan_tunnel off isolated off addrgenmode none numtxqueues 8 numrxqueues 8 gso_max_size 65536 gso_max_segs 65535
If I replace the cable with another cat 5e of another brand, having proper color wiring, the speed is stable at 1Gb/s.
Can the wrong color wiring be causing this issue, maybe do to EM interferences in the cable itself?
Or is it more likely to be the first cable that is low quality or so?