Introduction

NIC teaming presents an interesting solution to redundancy and high availability in the server/workstation computing realms. With the ability to have multiple network interface cards, an administrator can become creative in how a particular server accessed or create a larger pipe for traffic to flow through to the particular server.

This guide will walk through teaming of two network interface cards on a Debian 11 system. we will be using the the ifenslave package to attach and detach NICs from a bonded device.

The first thing to do before any configurations, is to determine the type of bonding that the system actually needs to implemented. There are six bonding modes supported by the Linux kernel as of this writing. Some of these bond 'modes' are simple to setup and others require special configurations on the switches in which the links connect.

Linux Bond Link Aggregation Modes

Install packages and load modules

ifenslave debian package - This is a tool to attach and detach slave network interfaces to a bonding device. A bonding device will act like a normal Ethernet network device to the kernel, but will send out the packets via the slave devices using a simple round-robin scheduler. This allows for simple load-balancing, identical to port-channel bonding or trunking techniques used in switches.

~] apt-get install ifenslave

Once the software installed, the kernel will need to_be told to load the bonding module both for this current installation as well as on future reboots.

~] echo 'bonding' >> /etc/modules
~] modprobe bonding

# if you want vlans:
~] echo '8021q' >> /etc/modules
~] modprobe 8021q
~] apt-get install vlan

Create the LACP 802.3ad bonded interface

Now that the kernel made aware of the necessary modules for NIC bonding, it is time to create the actual bonded interface. This is done through the interfaces file which is located at /etc/network/interfaces

This file contains the network interface settings for all of the network devices the system has connected. This example has two network cards (enp34s0f0 and enp34s0f1) attached to bond0 interface:

# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).

source /etc/network/interfaces.d/*

auto bond0
iface bond0 inet manual
        address 10.254.3.1/24
        bond-mode 802.3ad
        bond-slaves enp34s0f0 enp34s0f1
        bond-miimon 100
        bond-downdelay 200
        bond-updelay 400
        bond-lacp-rate 1
        up ifconfig bond0 10.254.3.1/24 up

The bond-mode 802.3ad) (you can use bond-mode 4) is what is used to determine which bond mode is used by this particular bonded interface. In this instance bond-mode 802.3ad indicates that this bond is an 802.3ad LACP) link aggregation.

Miimon is one of the options available for monitoring the status of bond links with the other option being the usage of arp requests. This guide will use miimon. bond-miimon 100 tells the kernel to inspect the link every 100 ms. bond-downdelay 200 means that the system will wait 200 ms before concluding that the currently active interface is indeed down. The bond-updelay 400 is used to tell the system to wait on using the new active interface until 400 ms after the link is brought up. most importantly, updelay and downdelay, both of these values must be multiples of the miimon value otherwise the system will round down.

Check the bonded interface status

~] cat /proc/net/bonding/bond0 
Ethernet Channel Bonding Driver: v5.10.0-9-amd64

Bonding Mode: IEEE 802.3ad Dynamic link aggregation
Transmit Hash Policy: layer2+3 (2)
MII Status: up
MII Polling Interval (ms): 100
Up Delay (ms): 400
Down Delay (ms): 200
Peer Notification Delay (ms): 0

802.3ad info
LACP rate: fast
Min links: 0
Aggregator selection policy (ad_select): stable
System priority: 65535
System MAC address: 00:1b:21:79:fe:8b
Active Aggregator Info:
        Aggregator ID: 3
        Number of ports: 1
        Actor Key: 9
        Partner Key: 17
        Partner Mac Address: 04:d5:90:77:69:76

Slave Interface: enp34s0f0
MII Status: up
Speed: 1000 Mbps
Duplex: full
Link Failure Count: 0
Permanent HW addr: 00:1b:21:79:fe:8b
Slave queue ID: 0
Aggregator ID: 3
Actor Churn State: none
Partner Churn State: none
Actor Churned Count: 0
Partner Churned Count: 0
details actor lacp pdu:
    system priority: 65535
    system mac address: 00:1b:21:79:fe:8b
    port key: 9
    port priority: 255
    port number: 1
    port state: 63
details partner lacp pdu:
    system priority: 65535
    system mac address: 04:d5:90:77:69:76
    oper key: 17
    port priority: 255
    port number: 2
    port state: 61

Slave Interface: enp34s0f1
MII Status: up
Speed: 1000 Mbps
Duplex: full
Link Failure Count: 0
Permanent HW addr: 00:1b:21:79:fe:8a
Slave queue ID: 0
Aggregator ID: 4
Actor Churn State: churned
Partner Churn State: none
Actor Churned Count: 1
Partner Churned Count: 0
details actor lacp pdu:
    system priority: 65535
    system mac address: 00:1b:21:79:fe:8b
    port key: 9
    port priority: 255
    port number: 2
    port state: 7
details partner lacp pdu:
    system priority: 65535
    system mac address: 04:d5:90:77:70:12
    oper key: 17
    port priority: 255
    port number: 2
    port state: 13

Sources

• https://unixcop.com/configure-bonding-and-teaming-on-debian-11/
• https://wiki.debian.org/Bonding
• https://www.claudiokuenzler.com/blog/1121/debian-11-bullseye-problem-bond-bonding-lacp-interfaces
• https://serverfault.com/questions/894828/linux-bond-mode-802-3ad-not-activated