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Linux server dual NIC bond(802.3ad) + switch LACP configuration

1. The principle of LACP

1. Basic concepts

Link Aggregation Control Protocol (LACP) is a subprotocol of the IEEE 802.3ad standard that provides a way to bundle multiple physical links into one logical link.

2. How it works

Protocol Interaction:

  • LACP negotiates by sending LACPDU (LACP Data Unit) packets
  • The devices at both ends exchange information such as system priority, system MAC, port priority, and port number
  • LACPDU is sent every second (FAST) or 30 seconds (SLOW).

Load Balancing:

  • Traffic is distributed based on the source MAC address, destination MAC address, source IP address, destination IP address, or TCP/UDP port
  • Ensure that the same data stream is always transmitted over the same physical link to avoid out-of-order packets

3. Advantages

  • Increase bandwidth: Multiple physical links work together
  • Link redundancy: A single link failure does not affect overall communication
  • Load balancing: Traffic is distributed across multiple physical links
  • Auto-negotiation: Dynamically detects the link status and automatically adjusts it

2. Configuration examples

1. Linux server configuration

Netplan configuration (Ubuntu 22.04):

network:
  version: 2
  renderer: networkd
  ethernets:
    eno1:
      dhcp4: no
      dhcp6: no
    eno2:
      dhcp4: no
      dhcp6: no
  bonds:
    bond0:
      interfaces: [eno1, eno2]
      parameters:
        mode: 802.3ad
        lacp-rate: fast
        transmit-hash-policy: layer3+4
        mii-monitor-interval: 100
      addresses:
        - 192.168.1.100/24
      routes:
        - to: default
          via: 192.168.1.1
      nameservers:
        addresses: [8.8.8.8, 114.114.114.114]
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2. Example switch configuration

Cisco Switches:

interface range GigabitEthernet1/0/1-2
 description LACP-to-Server
 switchport mode trunk
 channel-group 1 mode active
!
interface Port-channel1
 description LACP-Channel
 switchport mode trunk
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H3C Switches:

interface Bridge-Aggregation 1
 description LACP-Channel
 link-aggregation mode dynamic
!
interface GigabitEthernet1/0/1
 port link-aggregation group 1
!
interface GigabitEthernet1/0/2
 port link-aggregation group 1
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3. Precautions

1. Configuration requirements

  • Ensure that the NICs participating in the aggregation have the same rate
  • Switch port configurations must be consistent (rate, duplex, VLAN, etc.)
  • We recommend that you use a NIC of the same model for aggregation

2. Performance optimization

Choose the appropriate transmit-hash-policy:

  • layer 2: MAC address
  • layer3+4: IP+-based (recommended)
  • layer2+3: MAC+IP-based

Adjust the LACP update rate (lacp-rate):

  • fast: updates every second
  • slow: Updates every 30 seconds

3. Monitoring and Maintenance

Check the link status regularly:

cat /proc/net/bonding/bond0
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4. Frequently Asked Questions

Make sure the kernel loads the bonding module:

modprobe bonding
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Check the system logs to troubleshoot issues:

journalctl -u systemd-networkd
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Fourth, summary

Through core advantages such as link redundancy, load balancing, hot-swap support, and flexible configuration, LACP link aggregation technology can significantly improve network reliability, and is suitable for scenarios such as data center server connection, high-availability cluster node interconnection, high-bandwidth application servers, and core network equipment interconnection. The LACP dynamic aggregation mode is used to optimize the hash strategy based on the actual traffic characteristics, deploy the link status monitoring and alarm mechanism, and perform regular link health detection and maintenance, so as to build a high-availability and high-performance network infrastructure and provide continuous and stable underlying support for the business system.