Chapter 13. Network Interface Bonding

This chapter defines some of the bonding options you can use in your custom network configuration.

13.1. Network Interface Bonding and Link Aggregation Control Protocol (LACP)

You can bundle multiple physical NICs together to form a single logical channel known as a bond. Bonds can be configured to provide redundancy for high availability systems or increased throughput.

Red Hat OpenStack Platform supports Linux bonds, Open vSwitch (OVS) kernel bonds, and OVS-DPDK bonds.

The bonds can be used with the optional Link Aggregation Control Protocol (LACP). LACP is a negotiation protocol that creates a dynamic bond for load balancing and fault tolerance.

On any network that interacts directly with virtual machine instances, Red Hat recommends the use of OVS kernel bonds (bond type ovs_bond) or OVS-DPDK bonds (bond type ovs_dpdk_bond) with LACP. However, do not combine OVS kernel bonds and OVS-DPDK bonds on the same node.

On control and storage networks, Red Hat recommends the use of Linux bonds with VLAN and LACP, because OVS bonds carry the potential for control plane disruption that can occur when OVS or the neutron agent is restarted for updates, hot fixes, and other events. The Linux bond/LACP/VLAN configuration provides NIC management without the OVS disruption potential. Here is an example configuration of a Linux bond with one VLAN.


              - type: linux_bond
                name: bond_api
                bonding_options: "mode=active-backup"
                use_dhcp: false
        `          get_param: DnsServers
                - type: interface
                  name: nic3
                  primary: true
                - type: interface
                  name: nic4

              - type: vlan
                  get_param: InternalApiNetworkVlanID
                device: bond_api
                - ip_netmask:
                    get_param: InternalApiIpSubnet

13.2. Open vSwitch Bonding Options

The Overcloud provides networking through Open vSwitch (OVS). The following table describes support for OVS kernel and OVS-DPDK for bonded interfaces. The OVS/OVS-DPDK balance-tcp mode is available as a technology preview only.


This support requires Open vSwitch 2.9 or later.

OVS Bond mode



Compatible LACP options


High availability (active-passive)


active, passive, or off


Increased throughput (active-active)

  • Performance is affected by extra parsing per packet.
  • There is a potential for vhost-user lock contention.

active, passive, or off

balance-tcp (tech preview only )

Not recommended (active-active)

  • Recirculation needed for L4 hashing has a performance impact.
  • As with balance-slb, performance is affected by extra parsing per packet and there is a potential for vhost-user lock contention.
  • LACP must be enabled.

active or passive

You can configure a bonded interface in the network environment file using the BondInterfaceOvsOptions parameter as shown in this example:

  BondInterfaceOvsOptions: "bond_mode=balance-slb"

13.3. Linux bonding options

You can use LACP with Linux bonding in your network interface templates. For example:

      - type: linux_bond
        name: bond1
        - type: interface
          name: nic2
        - type: interface
          name: nic3
        bonding_options: "mode=802.3ad lacp_rate=[fast|slow] updelay=1000 miimon=100"
  • mode - enables LACP.
  • lacp_rate - defines whether LACP packets are sent every 1 second, or every 30 seconds.
  • updelay - defines the minimum amount of time that an interface must be active before it is used for traffic (this helps mitigate port flapping outages).
  • miimon - the interval in milliseconds that is used for monitoring the port state using the driver’s MIIMON functionality.

For more information on Linux bonding options, see 4.5.1. Bonding Module Directives in the Red Hat Enterprise Linux 7 Networking Guide.

13.4. General bonding options

The following table provides some explanation of these options and some alternatives depending on your hardware.

Table 13.1. Bonding Options


Balances flows based on source MAC address and output VLAN, with periodic rebalancing as traffic patterns change. Bonding with balance-slb allows a limited form of load balancing without the remote switch’s knowledge or cooperation. SLB assigns each source MAC and VLAN pair to a link and transmits all packets from that MAC and VLAN through that link. This mode uses a simple hashing algorithm based on source MAC address and VLAN number, with periodic rebalancing as traffic patterns change. This mode is similar to mode 2 bonds used by the Linux bonding driver. This mode can be used to provide load balancing even when the switch is not configured to use LACP.


This mode offers active/standby failover where the standby NIC resumes network operations when the active connection fails. Only one MAC address is presented to the physical switch. This mode does not require any special switch support or configuration, and works when the links are connected to separate switches. This mode does not provide load balancing.


Controls the Link Aggregation Control Protocol (LACP) behavior. Only certain switches support LACP. If your switch does not support LACP, use bond_mode=balance-slb or bond_mode=active-backup.


Sets the LACP behavior to switch to bond_mode=active-backup as a fallback.


Set the LACP heartbeat to 1 second (fast) or 30 seconds (slow). The default is slow.


Set the link detection to use miimon heartbeats (miimon) or monitor carrier (carrier). The default is carrier.


If using miimon, set the heartbeat interval in milliseconds.


Number of milliseconds a link must be up to be activated to prevent flapping.


Milliseconds between rebalancing flows between bond members. Set to zero to disable.