I wanted to know where is the documentation of channel bonding implementation in Ubuntu because the bonding modes are described differently on the internet

I have Ubuntu Server 10.0.4 LTS and it's using 2.6 kernel

Thank you


The Ubuntu documentation related to bonding modes is available here.

Descriptions of Ethernet bonding modes:

Mode 0


Round-robin policy: Transmit packets in sequential order from the first available slave through the last. This mode provides load balancing and fault tolerance.

Mode 1


Active-backup policy: Only one slave in the bond is active. A different slave becomes active if, and only if, the active slave fails. The bond's MAC address is externally visible on only one port (network adapter) to avoid confusing the switch. This mode provides fault tolerance. The primary option affects the behavior of this mode.

Mode 2


XOR policy: Transmit based on [(source MAC address XOR'd with destination MAC address) modulo slave count]. This selects the same slave for each destination MAC address. This mode provides load balancing and fault tolerance.

Mode 3


Broadcast policy: transmits everything on all slave interfaces. This mode provides fault tolerance.

Mode 4


IEEE 802.3ad Dynamic link aggregation. Creates aggregation groups that share the same speed and duplex settings. Utilizes all slaves in the active aggregator according to the 802.3ad specification.


  • Ethtool support in the base drivers for retrieving the speed and duplex of each slave.
  • A switch that supports IEEE 802.3ad Dynamic link aggregation. Most switches will require some type of configuration to enable 802.3ad mode.

Mode 5


Adaptive transmit load balancing: channel bonding that does not require any special switch support. The outgoing traffic is distributed according to the current load (computed relative to the speed) on each slave. Incoming traffic is received by the current slave. If the receiving slave fails, another slave takes over the MAC address of the failed receiving slave.


  • Ethtool support in the base drivers for retrieving the speed of each slave.

Mode 6


Adaptive load balancing: includes balance-tlb plus receive load balancing (rlb) for IPV4 traffic, and does not require any special switch support. The receive load balancing is achieved by ARP negotiation. The bonding driver intercepts the ARP Replies sent by the local system on their way out and overwrites the source hardware address with the unique hardware address of one of the slaves in the bond such that different peers use different hardware addresses for the server.

  • 1
    Thank you I already found this but it's not enough. I need something saying how each mode work in a much more specific way. – loo3y35 May 13 '14 at 4:49

I think that the best source is this Kernel.org document, it also provides explanations about when is each type optimal, and so on.

The sections are long, I only paste short excerpts:

11.2.1 HA Bonding Mode Selection for Multiple Switch Topology

In a topology such as the example above, the active-backup and broadcast modes are the only useful bonding modes when optimizing for availability; the other modes require all links to terminate on the same peer for them to behave rationally.

active-backup: This is generally the preferred mode, particularly if the switches have an ISL and play together well. If the network configuration is such that one switch is specifically a backup switch (e.g., has lower capacity, higher cost, etc), then the primary option can be used to insure that the preferred link is always used when it is available.

broadcast: This mode is really a special purpose mode, and is suitable only for very specific needs. For example, if the two switches are not connected (no ISL), and the networks beyond them are totally independent. In this case, if it is necessary for some specific one-way traffic to reach both independent networks, then the broadcast mode may be suitable.


12.1.1 MT Bonding Mode Selection for Single Switch Topology

This configuration is the easiest to set up and to understand, although you will have to decide which bonding mode best suits your needs. The trade offs for each mode are detailed below:

balance-rr: This mode is the only mode that will permit a single TCP/IP connection to stripe traffic across multiple interfaces. It is therefore the only mode that will allow a single TCP/IP stream to utilize more than one interface's worth of throughput. This comes at a cost, however: the striping generally results in peer systems receiving packets out of order, causing TCP/IP's congestion control system to kick in, often by retransmitting segments.


active-backup: There is not much advantage in this network topology to the active-backup mode, as the inactive backup devices are all connected to the same peer as the primary. In this case, a load balancing mode (with link monitoring) will provide the same level of network availability, but with increased available bandwidth. On the plus side, active-backup mode does not require any configuration of the switch, so it may have value if the hardware available does not support any of the load balance modes.

balance-xor: This mode will limit traffic such that packets destined for specific peers will always be sent over the same interface. Since the destination is determined by the MAC addresses involved, this mode works best in a "local" network configuration (as described above), with destinations all on the same local network. This mode is likely to be suboptimal if all your traffic is passed through a single router (i.e., a "gatewayed" network configuration, as described above).

As with balance-rr, the switch ports need to be configured for "etherchannel" or "trunking."

broadcast: Like active-backup, there is not much advantage to this mode in this type of network topology.

802.3ad: This mode can be a good choice for this type of network topology. The 802.3ad mode is an IEEE standard, so all peers that implement 802.3ad should interoperate well. The 802.3ad protocol includes automatic configuration of the aggregates, so minimal manual configuration of the switch is needed (typically only to designate that some set of devices is available for 802.3ad). The 802.3ad standard also mandates that frames be delivered in order (within certain limits), so in general single connections will not see misordering of packets. The 802.3ad mode does have some drawbacks: the standard mandates that all devices in the aggregate operate at the same speed and duplex. Also, as with all bonding load balance modes other than balance-rr, no single connection will be able to utilize more than a single interface's worth of bandwidth.


balance-tlb: The balance-tlb mode balances outgoing traffic by peer. Since the balancing is done according to MAC address, in a "gatewayed" configuration (as described above), this mode will send all traffic across a single device. However, in a "local" network configuration, this mode balances multiple local network peers across devices in a vaguely intelligent manner (not a simple XOR as in balance-xor or 802.3ad mode), so that mathematically unlucky MAC addresses (i.e., ones that XOR to the same value) will not all "bunch up" on a single interface.


balance-alb: This mode is everything that balance-tlb is, and more. It has all of the features (and restrictions) of balance-tlb, and will also balance incoming traffic from local network peers (as described in the Bonding Module Options section, above).

The only additional down side to this mode is that the network device driver must support changing the hardware address while the device is open.

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