Most modern Ethernet-based network interface cards (NICs), do not
require module parameters to alter settings. Instead, they can be
configured using ethtool or
mii-tool. Only after these tools fail to work
should module parameters be adjusted. Module paramaters can be viewed
using the modinfo command.
Note
For information about using these tools, consult the man pages for
ethtool, mii-tool, and
modinfo.
It is possible to use multiple Ethernet cards on a single machine. For
each card there must be an alias and, possibly,
options lines for each card in
/etc/modules.conf. Refer to the chapter titled
Kernel Modules in the
Red Hat Enterprise Linux System Administration Guide for more information.
Red Hat Enterprise Linux allows administrators to bind NICs together into a single
channel using the bonding kernel module and a
special network interface, called a channel bonding
interface. Channel bonding enables two or more network
interfaces to act as one, simultaneously increasing the bandwidth and
providing redundancy.
To channel bond multiple network interfaces, the
administrator must perform the following steps:
Add the following line to
/etc/modules.conf:
alias bond<N> bonding
Replace <N> with the interface
number, such as 0. For each configured
channel bonding interface, there must be a corresponding entry
in /etc/modules.conf.
To enhance performance, adjust available module options to
ascertain what combination works best. Pay particular attention to
the miimon or arp_interval
and the arp_ip_target parameters. Refer to
Section A.3.2.1 bonding Module Directives for a listing of
available options.
After testing, place preferred module options in
/etc/modules.conf.
Before finalizing the settings for the bonding
module, it is a good idea to test which settings work best. To do
this, open a shell prompt as root and type:
tail -f /var/log/messages
Open another shell prompt and use the
/sbin/insmod command to load the
bonding module with different parameters while
observing the kernel messages for errors.
The /sbin/insmod command is issued in the
following format:
/sbin/insmod bond<N><parameter=value>
Replace <N> with the number for the
bonding interface. Replace
<parameter=value> with a space
separated list of desired parameters for the interface.
Once satisfied that there are no errors and after verifying the
performance of the bonding interface, add the appropriate
bonding module parameters to
/etc/modules.conf.
The following is a list of available parameters for the
bonding module:
mode= — Specifies one of four
policies allowed for the bonding
module. Acceptable values for this parameter are:
0 — Sets a round-robin policy
for fault tolerance and load balancing. Transmissions are
received and sent out sequentially on each bonded slave
interface beginning with the first one available.
1 — Sets an active-backup
policy for fault tolerance. Transmissions are received and
sent out via the first available bonded slave
interface. Another bonded slave interface is only used if
the active bonded slave interface fails.
2 — Sets an XOR (exclusive-or) policy
for fault tolerance and load balancing. Using this method,
the interface matches up the incoming request's MAC address
with the MAC address for one of the slave NICs. Once this
link is established, transmissions are sent out sequentially
beginning with the first available interface.
3 — Sets a broadcast policy for
fault tolerance. All transmissions are sent on all slave interfaces.
4 — Sets an IEEE 802.3ad dynamic
link aggregation policy. Creates aggregation groups that
share the same speed and duplex settings. Transmits and
receives on all slaves in the active aggregator. Requires a
switch that is 802.3ad compliant.
5 — Sets a Transmit Load Balancing
(TLB) policy for fault tolerance and load balancing. The
outgoing traffic is distributed according to the current
load on each slave interface. Incoming traffic is received
by the current slave. If the receiving slave fails, another
slave takes over the MAC address of the failed slave.
6 — Sets an Active Load
Balancing (ALB) policy for fault tolerance and load
balancing. Includes transmit and receive load balancing for
IPV4 traffic. Receive load balancing is achieved through ARP
negotiation.
miimon= — Specifies (in
milliseconds) how often MII link monitoring occurs. This is
useful if high availability is required because MII is used to
verify that the NIC is active. To verify that the driver for a
particular NIC supports the MII tool, type the following command as
root:
ethtool <interface-name> | grep "Link detected:"
In this command, replace
<interface-name> with the name
of the device interface, such as eth0, not
the bond interface. If MII is supported, the
command returns:
Link detected: yes
If using a bonded interface for high availability, the module
for each NIC must support MII.
Setting the value to 0 (the default), turns
this feature off. When configuring this setting, a good starting
point for this parameter is 100.
downdelay= — Specifies (in
milliseconds) how long to wait after link failure before
disabling the link. The value must be a multiple of the value
specified in the miimon parameter. The value
is set to 0 by default, which
disables it.
updelay= — Specifies (in
milliseconds) how long to wait before enabling a link. The
value must be a multiple of the value specified in the
miimon parameter. The value is set to
0 by default, which
disables it.
arp_interval= — Specifies (in
milliseconds) how often ARP monitoring occurs.
If using this setting while in mode0 or 2 (the two
load-balancing modes), the network switch must be configured to
distribute packets evenly across the NICs. For more information
on how to accomplish this, refer to
The value is set to 0 by default, which
disables it.
arp_ip_target= — Specifies the
target IP address of ARP requests when the
arp_interval parameter is enabled. Up to 16
IP addresses can be specified in a comma separated list.
primary= — Specifies the interface
name, such as eth0, of the primary
device. The primary device is the first of
the bonding interfaces to be used and is not abandoned unless it
fails. This setting is particularly useful when one NIC in the
bonding interface is faster and, therefore, able to handle a
bigger load.
This setting is only valid when the bonding
interface is in active-backup mode. Refer to
multicast= — Specifies an integer
value for the type of multicast support desired.
Acceptable values for this parameter are:
0 — Disables multicast support.
1 — Enables multicast support,
but only on the active slave.
2 — Enables multicast support
on all slaves (the default).
Important
It is essential that either the arp_interval
and arp_ip_target or miimon
parameters are specified. Failure to due so can cause degradation
of network performance in the event a link fails.
