Intel igb network interface is down but still shows link up on the switch
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 version4.0.1-k
and firmware3.192
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