How to Configure Network Bonding on Linux
A complete walkthrough combining two or more network interfaces into a single bonded interface using NetworkManager — for redundancy, throughput, or both, depending on the mode you choose.
Network bonding combines multiple physical network interfaces into a single logical one — used for failover redundancy, aggregated throughput, or both, depending on which bonding mode is selected.
Step 1: understand the common bonding modes before choosing one
mode=active-backup — one interface active, the other standing by
purely for failover; no throughput gain
mode=802.3ad (LACP) — link aggregation requiring switch-side
support; combines bandwidth of all links
mode=balance-rr — round-robin across interfaces; needs no
special switch config but can reorder packetsChoosing the wrong mode for your actual goal (redundancy vs. throughput) is the most common source of “bonding isn’t doing what I expected.”
Step 2: check available interfaces
nmcli device statusStep 3: create the bond
sudo nmcli connection add type bond con-name bond0 ifname bond0 bond.options "mode=active-backup,miimon=100"miimon=100 checks link state every 100ms — necessary for the bond to actually detect a failed link and fail over promptly.
Step 4: add physical interfaces as bond members
sudo nmcli connection add type ethernet slave-type bond con-name bond0-port1 ifname eth0 master bond0
sudo nmcli connection add type ethernet slave-type bond con-name bond0-port2 ifname eth1 master bond0Step 5: configure the bond’s IP addressing
sudo nmcli connection modify bond0 ipv4.addresses 192.168.1.50/24 ipv4.gateway 192.168.1.1 ipv4.method manualStep 6: bring the bond up
sudo nmcli connection up bond0
sudo nmcli connection up bond0-port1
sudo nmcli connection up bond0-port2Step 7: verify bond status and active member interface
cat /proc/net/bonding/bond0This shows which interface is currently active (for active-backup mode), link state for each member, and overall bond health — the primary place to check when troubleshooting.
Step 8: test failover, for active-backup or LACP modes
sudo nmcli device disconnect eth0
cat /proc/net/bonding/bond0Confirm the bond fails over to the remaining interface and connectivity is maintained — testing this deliberately, before relying on it in production, is worth the few minutes it takes.
Step 9: coordinate LACP mode with switch-side configuration
For mode=802.3ad specifically, the switch ports the bonded interfaces connect to must be configured as an LACP-aggregated port group on the switch side too — a bond configured for LACP without matching switch configuration will not work correctly, and can behave worse than no bonding at all.
Why choosing the bonding mode deliberately matters more than the setup steps themselves
The actual configuration commands are nearly identical across modes — what differs is what each mode is for. Active-backup trades away throughput gains entirely in exchange for simplicity and zero switch-side dependency; LACP gets real throughput gains but requires the network team to configure the switch correctly too. Picking based on your actual goal, rather than defaulting to whichever mode a tutorial happened to use, is what determines whether the bond actually solves the problem you set out to solve.