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MC-LAG redundant connection

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MC-LAG (Multi-chassis link aggregation group) is a multi-chassis link aggregation technology. It provides a redundant connection to LAN and Internet access switches and increases infrastructure fault tolerance. For preconfigured servers, only the LAN connection can be reserved. Redundancy is not available for all configurations.

Configure MC-LAG only for servers whose configuration includes a redundant network card and MC-LAG.

For servers with an MC-LAG redundant connection, Selectel guarantees constant availability of one of the access switches, even during scheduled maintenance.

How it works

The server connects to two independent switches via an aggregated Ethernet channel (LAG, Etherchannel). The LACP 802.3ad protocol is used for the connection, and channel aggregation is configured on the server side. In this case, two links from the access switches to the server will be active simultaneously.

Connection speed

For servers of custom configuration:

  • 1 Gbit/s — copper crossover is used for the connection;
  • 10 Gbit/s — optical crossover is used for the connection;
  • 25 Gbit/s — LAN only; optical crossover is used for the connection.

For servers of prebuilt configuration:

  • 10 Gbit/s — for public network, optical crossover is used for the connection;
  • 10 Gbit/s — for LAN; optical crossover is used for the connection;
  • 25 Gbit/s — for LAN; optical crossover is used for the connection.

Cost

The cost of an MC-LAG redundant connection depends on the selected connection speed.

You can view the cost in the configurator on our website or when selecting server components in the Control Panel.

Configure MC-LAG

  1. Ensure the dedicated server configuration includes a redundant network card and that MC-LAG is added. If there is no redundant network card, you can order a new server with redundancy or change the components for a server of custom configuration.
  2. Wait for a server readiness message from technical support. The switch ports will be aggregated into a bond.
  3. Configure channel aggregation (LAG) on the server.

Configure channel aggregation on the server

Do not connect to the server via network interfaces that will be included in the aggregation. You will need to disable them during configuration.

  1. Connect to the server via a network interface that will not be included in the aggregation or via KVM console.

  2. Output information about the network interfaces:

    ip link

  3. Open the /etc/netplan/01-netcfg.yaml file:

    nano /etc/netplan/01-netcfg.yaml

  4. Set the settings for the network interfaces that will be included in the aggregation to the following:

    network:
      version: 2
      renderer: networkd
      ethernets:
        <eth_name_1>:
          dhcp4: false
        <eth_name_2>:
          dhcp4: false

      bonds:
        bond0:
          addresses:
            - <ip_address>/<mask>
          gateway4: <gateway_4>
          gateway6: <gateway_6>
          interfaces:
            - <eth_name_1>
            - <eth_name_2>
          # https://netplan.io/reference#properties-for-device-type-bonds
          parameters:
            mode: 802.3ad
            lacp-rate: fast
            transmit-hash-policy: layer3+4
            mii-monitor-interval: 100
            down-delay: 100
            up-delay: 100

    Specify:

    • <eth_name_1>, <eth_name_2> — names of the network interfaces to be included in the aggregation;
    • <ip_address> — IP address to be used on the aggregated interface;
    • <mask> — the subnet mask;
    • <gateway_4>, <gateway_6> — gateway.

  5. Apply the new configuration:

    netplan --debug apply

  6. Check that the bond0 network interface has been created correctly:

    cat /proc/net/bonding/bond0