ifenslave Command

The ifenslave command is used to attach and detach slave network interfaces to a bonding device in Linux. Bonding, also known as network interface aggregation or NIC teaming, is a method that allows multiple network interfaces to be aggregated into a single logical interface, providing redundancy and potentially increased throughput.

Basic Usage

ifenslave [OPTIONS] BOND_INTERFACE SLAVE_INTERFACE [SLAVE_INTERFACE...]

• BOND_INTERFACE: The bonding interface to which you want to attach or detach slave interfaces (e.g., bond0).

• SLAVE_INTERFACE: One or more network interfaces that you want to enslave (attach) to the bonding device.

Example Usage

1. Attach (enslave) interfaces to a bond

To attach eth0 and eth1 to a bonding interface called bond0:

sudo ifenslave bond0 eth0 eth1

This command adds both eth0 and eth1 as slaves to the bonding interface bond0.

2. Detach (release) a slave from a bond

To detach eth0 from the bond0 interface:

sudo ifenslave -d bond0 eth0

This command releases eth0 from the bonding interface.

Bonding Configuration

The bonding interface must first be created and configured in the system. Here is a basic setup for bonding:

1. Create the bond interface configuration in /etc/network/interfaces (Debian/Ubuntu) or the appropriate configuration files in your distribution.

# Example for Debian/Ubuntu /etc/network/interfaces
auto bond0
iface bond0 inet static
    address 192.168.1.10
    netmask 255.255.255.0
    bond-slaves eth0 eth1
    bond-mode 802.3ad
    bond-miimon 100
    bond-lacp-rate fast

• bond-mode: Specifies the bonding mode. Common modes include:

  • balance-rr: Round-robin (transmission load balancing).

  • active-backup: Only one slave is active, others are backup.

  • balance-xor: XOR hashing for load balancing.

  • 802.3ad: IEEE 802.3ad dynamic link aggregation (LACP).

• bond-miimon: Specifies the monitoring frequency (in milliseconds) to check the status of each slave.

• bond-lacp-rate: Specifies the rate of LACP packets (used for 802.3ad mode).

1. Restart networking services or use the ifup command to activate the configuration.

sudo ifup bond0

3. View bonding status

To see the current bonding status, including which slaves are attached and their statuses:

cat /proc/net/bonding/bond0

This will show details about the bonding interface, such as active slaves, bonding mode, and link status of each interface.

Bonding Modes

• balance-rr (0): Round-robin policy, traffic is transmitted in order across all slaves, providing load balancing and fault tolerance.

• active-backup (1): Only one slave is active at a time. If the active interface fails, another slave is activated. This provides fault tolerance.

• balance-xor (2): Transmit based on XOR of source and destination MAC addresses, provides load balancing and fault tolerance.

• broadcast (3): Sends traffic on all slaves, providing fault tolerance.

• 802.3ad (4): IEEE 802.3ad Dynamic link aggregation. Requires a switch that supports Link Aggregation Control Protocol (LACP).

• balance-tlb (5): Adaptive transmit load balancing, dynamically balances outgoing traffic based on the load on each slave.

• balance-alb (6): Adaptive load balancing, includes both transmit and receive load balancing for IPv4 traffic.

Conclusion

The ifenslave command is an essential tool for managing bonded interfaces in Linux. It allows you to easily attach and detach network interfaces to a bond, enabling network redundancy and load balancing. Bonding interfaces, when configured correctly, can improve network performance and reliability in environments where high availability is a priority.