Network bonding combines multiple physical network interfaces into a single logical one — for redundancy, increased throughput, or both, depending on the bonding mode chosen.
# Ubuntu netplan example: active-backup bonding for redundancy
network:
version: 2
bonds:
bond0:
interfaces: [eth0, eth1]
parameters:
mode: active-backup
primary: eth0
addresses: [192.168.1.50/24]
routes:
- to: default
via: 192.168.1.1
Bonding Modes That Matter
- active-backup — one interface active, the other a hot standby; pure redundancy, no throughput gain
- 802.3ad (LACP) — aggregates bandwidth across interfaces, requires switch-side configuration to match
- balance-rr — round-robins packets across interfaces; simple but can cause out-of-order delivery for some protocols
LACP mode requires the connected switch to also be configured for link aggregation on those specific ports — bonding is configured on both ends of the connection, not just the Linux server side, and mismatched configuration on either side will cause the bond to fail or perform poorly.