Intel igb network interface is down but still shows link up on the switch

Solution Unverified - Updated -

Issue

  • Our Intel igb-based interfaces can be set down, but still show link up on the switch:
hostname# ip link show dev eth2 | grep mtu
4: eth2: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP qlen 1000
hostname# ethtool eth2 | grep detected
        Link detected: yes

switch-> show interfaces 1/23
 Slot/Port  1/23 :
  Operational Status     : up,

hostname# ip link set eth2 down
hostname# ip link show dev eth2 | grep mtu
4: eth2: <BROADCAST,MULTICAST> mtu 1500 qdisc mq state DOWN qlen 1000
hostname# ethtool eth2 | grep detect
        Link detected: no

switch-> show interfaces 1/23
 Slot/Port  1/23 :
  Operational Status     : up,
  • This was reviewed by someone from our hardware team, and it seems that this issue is caused by a specific hardware configuration (a config bit in the MANC register of the EEPROM) that retains power to the PHY even when the interface is taken down to support SOL (Serial-Over-LAN).

  • Is there a way to change/override this behavior in the driver from the OS?

Environment

  • Red Hat Enterprise Linux 6.4
  • Intel network interface with igb driver version 4.0.1-k and firmware 3.192

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