Interface Bonding

Document revision:1.2 (September 10, 2007, 14:35 GMT)
Applies to: V3.0

General Information


Bonding is a technology that allows to aggregate multiple ethernet-like interfaces into a single virtual link, thus getting higher data rates and providing failover.

Quick Setup Guide

Let us assume that we have 2 NICs in each router (Router1 and Router2) and want to get maximum data rate between 2 routers. To make this possible, follow these steps:

  1. Make sure that you do not have IP addresses on interfaces which will be enslaved for bonding interface!
  2. Add bonding interface on Router1:

    [admin@Router1] interface bonding> add slaves=ether1,ether2

    And on Router2:

    [admin@Router2] interface bonding> add slaves=ether1,ether2
  3. Add addresses to bonding interfaces:

    [admin@Router1] ip address> add address= interface=bonding1
    [admin@Router2] ip address> add address= interface=bonding1
  4. Test the link from Router1:

    [admin@Router1] interface bonding> /pi ping timeout ping timeout ping timeout 64 byte ping: ttl=64 time=2 ms 64 byte ping: ttl=64 time=2 ms

    Note that bonding interface needs a couple of seconds to get connectivity with its peer.


Packages required: system
License required: Level1
Submenu level: /interface bonding
Standards and Technologies: None
Hardware usage: Not significant

Related Documents


To provide a proper failover, you should specify link-monitoring parameter. It can be:

link-monitoring is used to check whether the link is up or not.

Property Description

arp (disabled | enabled | proxy-arp | reply-only; default: enabled) - Address Resolution Protocol for the interface
disabled - the interface will not use ARP
enabled - the interface will use ARP
proxy-arp - the interface will use the ARP proxy feature
reply-only - the interface will only reply to the requests originated to its own IP addresses. Neighbour MAC addresses will be resolved using /ip arp statically set table only

arp-interval (time; default: 00:00:00.100) - time in milliseconds which defines how often to monitor ARP requests

arp-ip-targets (IP address; default: "") - IP target address which will be monitored if link-monitoring is set to arp. You can specify multiple IP addresses, separated by comma

down-delay (time; default: 00:00:00) - if a link failure has been detected, bonding interface is disabled for down-delay time. Value should be a multiple of mii-interval

lacp-rate (1sec | 30secs; default: 30secs) - Link Aggregation Control Protocol rate specifies how often to exchange with LACPDUs between bonding peer. Used to determine whether link is up or other changes have occured in the network. LACP tries to adapt to these changes providing failover.

link-monitoring (arp | mii-type1 | mii-type2 | none; default: none) - method to use for monitoring the link (whether it is up or down)
arp - uses Address Resolution Protocol to determine whether the remote interface is reachable
mii-type1 - uses Media Independent Interface type1 to determine link status. Link status determenation relies on the device driver. If bonding shows that the link status is up, when it should not be, then it means that this card don't support this possibility.
mii-type2 - uses MII type2 to determine link status (used if mii-type1 is not supported by the NIC)
none - no method for link monitoring is used. If a link fails, it is not considered as down (but no traffic passes through it, thus).

mac-address (read-only: MAC address) - MAC address of the bonding interface

mii-interval (time; default: 00:00:00.100) - how often to monitor the link for failures (parameter used only if link-monitoring is mii-type1 or mii-type2)

mode (802.3ad | active-backup | balance-alb | balance-rr | balance-tlb | balance-xor | broadcast; default: balance-rr) - interface bonding mode. Can be one of:
802.3ad - IEEE 802.3ad dynamic link aggregation. In this mode, the interfaces are aggregated in a group where each slave shares the same speed. If you use a switch between 2 bonding routers, be sure that this switch supports IEEE 802.3ad standard. Provides fault tolerance and load balancing.
active-backup - provides link backup. Only one slave can be active at a time. Another slave becomes active only, if first one fails.
balance-alb - adaptive load balancing. It includes balance-tlb and received traffic is also balanced. Device driver should support for setting the mac address, then it is active. Otherwise balance-alb doesn't work. No special switch is required.
balance-rr - round-robin load balancing. Slaves in bonding interface will transmit and receive data in sequential order. Provides load balancing and fault tolerance.
balance-tlb - Outgoing traffic is distributed according to the current load on each slave. Incoming traffic is received by the current slave. If receiving slave fails, then another slave takes the MAC address of the failed slave. Doesn't require any special switch support.
balance-xor - Use XOR policy for transmit. Provides only failover (in very good quality), but not load balancing, yet.
broadcast - Broadcasts the same data on all interfaces at once. This provides fault tolerance but slows down traffic throughput on some slow machines.

mtu (integer: 68..1500; default: 1500) - Maximum Transmit Unit in bytes

name (name) - descriptive name of bonding interface

primary (name; default: none) - Interface is used as primary output media. If primary interface fails, only then others slaves will be used. This value works only with mode=active-backup

slaves (name) - at least two ethernet-like interfaces separated by a comma, which will be used for bonding

up-delay (time; default: 00:00:00) - if a link has been brought up, bonding interface is disabled for up-delay time and after this time it is enabled. Value should be a multiple of mii-interval


Link failure detection and failover is working significantly better with expensive network cards, for example, made by Intel, then with more cheap ones. For example, on Intel cards failover is taking place in less than a second after link loss, while on some other cards, it may require up to 20 seconds. Also, the Active load balancing (mode=balance-alb) does not work on some cheap cards.

Application Examples

Bonding two Eoip tunnels

Assume you need to configure the MikroTik router for the following network setup, where you have two offices with 2 ISP for each. You want combine links for getting double speed and provide failover:

We are assuming that connections to Internet through two ISP are configured for both routers.