Intel Ethernet X520 10GbE Dual Port KX4 Mezz User Manual page 71

Allocating Rx Buffers when Using Jumbo Frames
Allocating Rx buffers when using Jumbo Frames on 2.6.x kernels may fail if the available memory is heavily frag-
mented. This issue may be seen with PCI-X adapters or with packet split disabled. This can be reduced or eliminated
by changing the amount of available memory for receive buffer allocation, by increasing /proc/sys/vm/min_free_kbytes.
Multiple Interfaces on Same Ethernet Broadcast Network
Due to the default ARP behavior on Linux, it is not possible to have one system on two IP networks in the same Eth-
ernet broadcast domain (non-partitioned switch) behave as expected. All Ethernet interfaces will respond to IP traffic for
any IP address assigned to the system. This results in unbalanced receive traffic.
If you have multiple interfaces in a server, turn on ARP filtering by entering:
echo 1 > /proc/sys/net/ipv4/conf/all/arp_filter
(this only works if your kernel's version is higher than 2.4.5).
NOTE: This setting is not saved across reboots. However, this configuration change can be made permanent
through one of the following methods:
Add the following line to /etc/sysctl.conf:
l
net.ipv4.conf.all.arp_filter = 1
Install the interfaces in separate broadcast domains (either in different switches or in a switch partitioned
l
to VLANs).
Disable Rx Flow Control with ethtool
In order to disable receive flow control using ethtool, you must turn off auto-negotiation on the same command line. For
example:
ethtool -A eth? autoneg off rx off
Unplugging Network Cable While ethtool -p is Running
In kernel versions 2.5.50 and later (including 2.6 kernel), unplugging the network cable while ethtool -p is running will
cause the system to become unresponsive to keyboard commands, except for control-alt-delete. Restarting the system
appears to be the only remedy.
MSI-X Issues with Kernels Between 2.6.19 and 2.6.21 (inclusive)
Kernel panics and instability may be observed on any MSI-X hardware if you use irqbalance with kernels between
2.6.19 and 2.6.21. If these types of problems are encountered, you may disable the irqbalance daemon or upgrade to a
newer kernel.
Rx Page Allocation Errors
Page allocation failure order:0 errors may occur under stress with kernels 2.6.25 and above. This is caused by the way
the Linux kernel reports this stressed condition.
Activity LED Blinks Unexpectedly
If a system based on the 82577, 82578, or 82579 controller is connected to a hub, the Activity LED will blink for all net-
work traffic present on the hub. Connecting the system to a switch or router will filter out most traffic not addressed to
the local port.
Link May Take Longer Than Expected
With some PHY and switch combinations, link can take longer than expected. This can be an issue on Linux dis-
tributions that timeout when checking for link prior to acquiring a DHCP address; however, there is usually a way to
work around this (for example, set LINKDELAY in the interface configuration on RHEL).