Configure network interface bonding with LACP and failover for enterprise networking

Install bonding kernel module

Load the bonding kernel module and ensure it loads on boot for network interface bonding support.

sudo modprobe bonding
echo "bonding" | sudo tee -a /etc/modules

Configure bonding with NetworkManager

NetworkManager provides the most reliable method for configuring LACP bonding on modern Linux distributions. Create the bond interface first.

sudo nmcli connection add type bond con-name bond0 ifname bond0 bond.options "mode=802.3ad,miimon=100,lacp_rate=fast,xmit_hash_policy=layer2+3"

Add slave interfaces to the bond

Add your physical network interfaces as slaves to the bond. Replace ens3 and ens4 with your actual interface names.

sudo nmcli connection add type ethernet slave-type bond con-name bond0-slave1 ifname ens3 master bond0
sudo nmcli connection add type ethernet slave-type bond con-name bond0-slave2 ifname ens4 master bond0

Configure IP addressing for the bond

Set up static IP configuration for the bonded interface. Adjust the IP address, gateway, and DNS servers for your network.

sudo nmcli connection modify bond0 ipv4.addresses 203.0.113.10/24
sudo nmcli connection modify bond0 ipv4.gateway 203.0.113.1
sudo nmcli connection modify bond0 ipv4.dns "203.0.113.1,8.8.8.8"
sudo nmcli connection modify bond0 ipv4.method manual

Activate the bonded interface

Bring up the bond interface and its slave interfaces to establish the LACP aggregation.

sudo nmcli connection up bond0-slave1
sudo nmcli connection up bond0-slave2
sudo nmcli connection up bond0

Alternative systemd-networkd configuration

For systems using systemd-networkd instead of NetworkManager, create these configuration files for LACP bonding.

[NetDev]
Name=bond0
Kind=bond

[Bond]
Mode=802.3ad
LACPTransmitRate=fast
MIIMonitorSec=100ms
TransmitHashPolicy=layer2+3

Configure bond network settings

Create the network configuration file for the bonded interface with IP addressing.

[Match]
Name=bond0

[Network]
Address=203.0.113.10/24
Gateway=203.0.113.1
DNS=203.0.113.1
DNS=8.8.8.8

Configure slave interfaces for systemd-networkd

Create configuration files for each physical interface that will be part of the bond.

[Match]
Name=ens3

[Network]
Bond=bond0

[Match]
Name=ens4

[Network]
Bond=bond0

Enable systemd-networkd

If using systemd-networkd configuration, enable and restart the networking service.

sudo systemctl enable systemd-networkd
sudo systemctl restart systemd-networkd

Create network monitoring script

This script monitors bond status and logs failover events for troubleshooting and validation.

#!/bin/bash
BOND_INTERFACE="bond0"
LOG_FILE="/var/log/bond-monitor.log"

while true; do
    BOND_STATUS=$(cat /proc/net/bonding/$BOND_INTERFACE 2>/dev/null)
    ACTIVE_SLAVE=$(echo "$BOND_STATUS" | grep "Currently Active Slave" | awk '{print $4}')
    SLAVE_COUNT=$(echo "$BOND_STATUS" | grep -c "Slave Interface:")
    
    echo "$(date): Bond $BOND_INTERFACE - Active: $ACTIVE_SLAVE, Slaves: $SLAVE_COUNT" >> $LOG_FILE
    
    if [ $SLAVE_COUNT -lt 2 ]; then
        logger "WARNING: Bond $BOND_INTERFACE has only $SLAVE_COUNT active slaves"
    fi
    
    sleep 30
done

sudo chmod 755 /usr/local/bin/monitor-bond.sh

Create systemd service for monitoring

Set up a systemd service to run the bond monitoring script continuously.

[Unit]
Description=Network Bond Monitor
After=network.target

[Service]
Type=simple
ExecStart=/usr/local/bin/monitor-bond.sh
Restart=always
User=root

[Install]
WantedBy=multi-user.target

sudo systemctl enable bond-monitor.service
sudo systemctl start bond-monitor.service

Test failover functionality

Simulate interface failure to verify LACP failover works correctly. Run these tests during maintenance windows.

# Test by disabling one interface
sudo ip link set ens3 down

Check bond status
cat /proc/net/bonding/bond0

Test connectivity
ping -c 5 203.0.113.1

Re-enable interface
sudo ip link set ens3 up

Check LACP partner information

Verify that LACP negotiation is working between your server and the switch.

# Check detailed bond status
sudo cat /proc/net/bonding/bond0 | grep -A 10 "Partner Mac Address"

Check for LACP PDU transmission
sudo tcpdump -i ens3 ether proto 0x8809 -v

Verify bonding module parameters

Check that the bonding module loaded with correct parameters for LACP operation.

# Check loaded bonding parameters
sudo modinfo bonding

Verify bond mode and options
grep -r bond /sys/class/net/bond0/bonding/