Chapter 13. Network Interface Bonding

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

13.1. Open vSwitch Bonding Options

The Overcloud provides networking through Open vSwitch (OVS), which provides several options for bonded interfaces. You can configure a bonded interface in the network environment file using the following parameter: 

parameter_defaults:
  BondInterfaceOvsOptions: "bond_mode=balance-slb"
Important

By default, you cannot use LACP with OVS-based bonds. This configuration is not supported due to a known issue with some versions of Open vSwitch. Instead, consider using bond_mode=balance-slb as a replacement for this functionality. For the technical details behind this constraint, see BZ#1267291.

13.2. Linux bonding options

By default, you cannot use LACP with OVS-based bonds. However, you can use LACP with Linux bonding in your network interface templates. For example: 

      - type: linux_bond
        name: bond1
        members:
        - 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.

After you delete the constraint from each NIC file, you can set the bond mode option in the bond interface parameter:

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

13.3. General bonding options

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

Table 13.1. Bonding Options

bond_mode=balance-slb

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 is used when the switch is configured with bonding but is not configured to use LACP (static instead of dynamic bonds).

bond_mode=active-backup

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.

lacp=[active|passive|off]

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.

other-config:lacp-fallback-ab=true

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

other_config:lacp-time=[fast|slow]

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

other_config:bond-detect-mode=[miimon|carrier]

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

other_config:bond-miimon-interval=100

If using miimon, set the heartbeat interval in milliseconds.

other_config:bond_updelay=1000

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

other_config:bond-rebalance-interval=10000

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

Important

If you experience packet drops or performance issues using Linux bonds with Provider networks, consider disabling Large Receive Offload (LRO) on the standby interfaces. Avoid adding a Linux bond to an OVS bond, as port-flapping and loss of connectivity can occur. This is a result of a packet-loop through the standby interface.