How to Configure Network Bonding on AlmaLinux

Network bonding is a method of combining multiple network interfaces into a single logical interface to increase bandwidth, improve redundancy, and ensure high availability. It is particularly useful in server environments where uninterrupted network connectivity is critical. AlmaLinux, a robust enterprise-grade Linux distribution, provides built-in support for network bonding, making it a preferred choice for setting up reliable and scalable network configurations.

This guide explains how to configure network bonding on AlmaLinux, step by step.

Why Use Network Bonding?

Network bonding offers several advantages:

1. Increased Bandwidth: Combines the bandwidth of multiple network interfaces.
2. High Availability: Provides fault tolerance by redirecting traffic to functional interfaces if one fails.
3. Load Balancing: Distributes traffic evenly across interfaces, optimizing performance.
4. Simplified Configuration: Offers centralized management for multiple physical interfaces.

Prerequisites

Before you begin, ensure you have the following:

1. AlmaLinux Installed: A fresh or existing AlmaLinux installation with administrative access.
2. Multiple Network Interfaces: At least two NICs (Network Interface Cards) for bonding.
3. Root or Sudo Access: Required for network configuration.
4. Stable Internet Connection: For installing necessary packages.

Step 1: Update Your System

Always start by updating your system to ensure you have the latest updates and bug fixes:

sudo dnf update -y

This ensures the latest network management tools are available.

Step 2: Verify Network Interfaces

Identify the network interfaces you want to include in the bond. Use the ip command to list all available interfaces:

ip link show

You’ll see a list of interfaces like this:

1: lo: <LOOPBACK,UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
2: enp0s3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
3: enp0s8: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000

Note the names of the interfaces you plan to bond (e.g., enp0s3 and enp0s8).

Step 3: Install Required Tools

Ensure the NetworkManager package is installed. It simplifies managing network configurations, including bonding:

sudo dnf install -y NetworkManager

Step 4: Create a Bond Interface

Create a bond interface using nmcli, the command-line tool for managing networks.

Add the Bond Interface

Run the following command to create a bond interface named bond0:

sudo nmcli connection add type bond con-name bond0 ifname bond0 mode active-backup

• bond0: The name of the bond interface.
• active-backup: The bonding mode. Other modes include balance-rr, balance-xor, and 802.3ad.

Step 5: Add Slave Interfaces to the Bond

Add the physical interfaces (e.g., enp0s3 and enp0s8) as slaves to the bond:

sudo nmcli connection add type bond-slave con-name bond0-slave1 ifname enp0s3 master bond0
sudo nmcli connection add type bond-slave con-name bond0-slave2 ifname enp0s8 master bond0

• bond0-slave1 and bond0-slave2: Names for the slave connections.
• enp0s3 and enp0s8: Names of the physical interfaces.

Step 6: Configure IP Address for the Bond

Assign an IP address to the bond interface. You can configure either a static IP address or use DHCP.

Static IP Address

To assign a static IP, use the following command:

sudo nmcli connection modify bond0 ipv4.addresses 192.168.1.100/24 ipv4.method manual
sudo nmcli connection modify bond0 ipv4.gateway 192.168.1.1
sudo nmcli connection modify bond0 ipv4.dns 8.8.8.8

Replace 192.168.1.100/24 with your desired IP address and subnet mask, 192.168.1.1 with your gateway, and 8.8.8.8 with your preferred DNS server.

Dynamic IP Address (DHCP)

To use DHCP:

sudo nmcli connection modify bond0 ipv4.method auto

Step 7: Activate the Bond Interface

Activate the bond and slave interfaces to apply the configuration:

sudo nmcli connection up bond0
sudo nmcli connection up bond0-slave1
sudo nmcli connection up bond0-slave2

Verify the status of the bond interface:

nmcli connection show bond0

Step 8: Verify Network Bonding

Check Bond Status

Use the following command to verify the bond status and its slave interfaces:

cat /proc/net/bonding/bond0

The output provides detailed information, including:

• Active bonding mode.
• Status of slave interfaces.
• Link status of each interface.

Check Connectivity

Test network connectivity by pinging an external host:

ping -c 4 8.8.8.8

Test Failover

Simulate a failover by disconnecting one of the physical interfaces and observing if traffic continues through the remaining interface.

Step 9: Make the Configuration Persistent

The nmcli tool automatically saves the configurations, ensuring they persist across reboots. To confirm, restart your system:

sudo reboot

After the reboot, verify that the bond interface is active:

nmcli connection show bond0

Step 10: Advanced Bonding Modes

AlmaLinux supports several bonding modes. Here’s a summary of the most common ones:

1. active-backup:

   • Only one interface is active at a time.
   • Provides fault tolerance and failover capabilities.

2. balance-rr:

   • Sends packets in a round-robin fashion across all interfaces.
   • Increases throughput but requires switch support.

3. balance-xor:

   • Distributes traffic based on the source and destination MAC addresses.
   • Requires switch support.

4. 802.3ad (LACP):

   • Implements the IEEE 802.3ad Link Aggregation Control Protocol.
   • Provides high performance and fault tolerance but requires switch support.

5. broadcast:

   • Sends all traffic to all interfaces.
   • Useful for specific use cases like network redundancy.

To change the bonding mode, modify the bond configuration:

sudo nmcli connection modify bond0 bond.options "mode=802.3ad"

Restart the bond interface:

sudo nmcli connection up bond0

Step 11: Troubleshooting

Here are common issues and their solutions:

1. Bond Interface Fails to Activate:

   • Ensure all slave interfaces are not managed by other connections.
   • Check for typos in interface names.

2. No Internet Connectivity:

   • Verify the IP address, gateway, and DNS configuration.
   • Ensure the bond interface is properly linked to the network.

3. Failover Not Working:

   • Confirm the bonding mode supports failover.
   • Check the status of slave interfaces in /proc/net/bonding/bond0.

4. Switch Configuration Issues:

   • For modes like 802.3ad, ensure your network switch supports and is configured for link aggregation.

Conclusion

Configuring network bonding on AlmaLinux enhances network reliability and performance, making it an essential skill for system administrators. By following this guide, you’ve successfully set up a bonded network interface, optimized for high availability, failover, and load balancing. Whether you’re managing enterprise servers or personal projects, network bonding ensures a robust and efficient network infrastructure.

With AlmaLinux’s stability and built-in support for bonding, you can confidently deploy reliable network configurations to meet your specific requirements.