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q32-bonding-and-bridges

Énoncé§

Solve this question on: data-002

Create a network bond bond0 aggregating eth1 and eth2 in active-backup mode.
Assign IP 10.0.0.5/24 to bond0.
Create a bridge br0 containing eth3, with IP 10.0.1.1/24, so virtual machines can attach to it.

Solution§

Bond modes§

Mode	Name	Behaviour
0	`balance-rr`	round-robin across slaves
1	`active-backup`	one slave active, others standby — most reliable
2	`balance-xor`	XOR hash for outgoing frames
3	`broadcast`	every frame on every slave
4	`802.3ad`	LACP — needs switch support
5	`balance-tlb`	adaptive transmit load balancing
6	`balance-alb`	adaptive load balancing (TX + RX)

Step 1 — Bonding with nmcli§

sudo nmcli con add type bond ifname bond0 con-name bond0 mode active-backup
sudo nmcli con mod bond0 ipv4.addresses 10.0.0.5/24 ipv4.method manual
sudo nmcli con mod bond0 +bond.options "miimon=100,primary=eth1"

sudo nmcli con add type ethernet ifname eth1 master bond0 con-name bond-eth1
sudo nmcli con add type ethernet ifname eth2 master bond0 con-name bond-eth2

sudo nmcli con up bond-eth1
sudo nmcli con up bond-eth2
sudo nmcli con up bond0

Inspect:

cat /proc/net/bonding/bond0
ip -br link

Step 1bis — Bonding by hand (no NM)§

Load the module + create the master:

sudo modprobe bonding
echo "+bond0" | sudo tee /sys/class/net/bonding_masters

# configure mode BEFORE adding slaves
echo active-backup | sudo tee /sys/class/net/bond0/bonding/mode
echo 100           | sudo tee /sys/class/net/bond0/bonding/miimon

sudo ip link set eth1 down
sudo ip link set eth2 down
echo "+eth1" | sudo tee /sys/class/net/bond0/bonding/slaves
echo "+eth2" | sudo tee /sys/class/net/bond0/bonding/slaves

sudo ip addr add 10.0.0.5/24 dev bond0
sudo ip link set bond0 up

Make persistent: drop a config under /etc/modules-load.d/bonding.conf with bonding and a NetworkManager / netplan / networkd profile as above.

Step 2 — Netplan equivalent for the bond§

network:
  version: 2
  renderer: networkd
  ethernets:
    eth1: {dhcp4: no}
    eth2: {dhcp4: no}
  bonds:
    bond0:
      interfaces: [eth1, eth2]
      addresses: [10.0.0.5/24]
      parameters:
        mode: active-backup
        primary: eth1
        mii-monitor-interval: 100

Step 3 — Bridge§

sudo nmcli con add type bridge ifname br0 con-name br0
sudo nmcli con mod br0 ipv4.addresses 10.0.1.1/24 ipv4.method manual
sudo nmcli con mod br0 bridge.stp no

sudo nmcli con add type ethernet ifname eth3 master br0 con-name br-eth3
sudo nmcli con up br-eth3
sudo nmcli con up br0

Manual variant with ip:

sudo ip link add name br0 type bridge
sudo ip link set br0 up
sudo ip link set eth3 master br0
sudo ip addr add 10.0.1.1/24 dev br0

Inspect:

bridge link show
ip -br link show master br0
brctl show                     # legacy tool, still common

Netplan bridge example:

network:
  version: 2
  bridges:
    br0:
      interfaces: [eth3]
      addresses: [10.0.1.1/24]
      parameters:
        stp: false

VLAN (often paired in exams)§

sudo ip link add link eth0 name eth0.10 type vlan id 10
sudo ip addr add 192.168.10.5/24 dev eth0.10
sudo ip link set eth0.10 up

Persistent (nmcli):

nmcli con add type vlan con-name eth0.10 dev eth0 id 10 ip4 192.168.10.5/24

—The Gardener