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MC-LAG redundant connection
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MC-LAG redundant connection

MC-LAG (Multi-chassis link aggregation group) — Multi-chassis link aggregation. Redundant connectivity to LAN and Internet access switches, improves infrastructure fault tolerance. Only LAN connectivity can be reserved for prebuilt configuration servers. Redundancy is not available for all configurations.

Configure MC-LAG is only available for servers that have a redundant NIC and MC-LAG in their configuration.

For servers with redundant MC-LAG connectivity, Selectel ensures that one of the access switches is always available, including during scheduled maintenance.

Working principle

The server connects to two independent switches over an aggregated Ethernet link (LAG, Etherchannel). The LACP 802.3ad protocol is used for connectivity and link aggregation is configured on the server side. In this case, two links from the access switches to the server will be active at the same time.

Connection speed

For [custom configuration] servers(/servers-and-infrastructure/dedicated/order/dedicated-configurations/#servers-arbitrary-configurations):

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

For servers ready-configuration:

  • 10 Gbit/sec — for LAN only, optical crossover is used for connection.


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

You can view the cost in the configurator on the website, or when selecting server accessories in control panel.

Customize MC-LAG

  1. Ensure that the dedicated server configuration has a redundant NIC and MC-LAG added. If a redundant NIC is not available, you can order a new redundant server or modify the components for a server of a custom configuration.
  2. Wait for a server readiness message from technical support. The switch ports will be bonded together.
  3. Configure link aggregation (LAG) on the server.

Configure channel aggregation on the server

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

  1. Connect to the server on a network interface that will not be included in the aggregation, or through KVM-console.

  2. Check that the bonding kernel module is installed on the server:

    lsmod | grep bond

    If there is no information in the response — the bonding kernel module is not installed.

  3. If the bonding kernel module is not installed, install it:

    sudo modprobe bonding
  4. Install a package to manage and configure interfaces for parallel routing (bonding):

    apt-get install ifenslave
  5. Output the data about the network interfaces:

    ifconfig -a
  6. Consecutively shut down each network interface that will be included in the aggregation:

    ifdown <eth_name>

    Specify <eth_name> is the interface name.

  7. Open the /etc/network/interfaces file:

    nano /etc/network/interfaces
  8. Bring the settings for the network interfaces that will be included in the aggregation to the following:

    source /etc/network/interfaces
    auto lo
    iface lo inet loopback

    auto <eth_name_1>
    iface <eth_name_1> inet static
    bond-master bond0
    bond-primary <eth_name_1> <eth_name_2>

    auto <eth_name_2>
    iface <eth_name_2> inet manual
    bond-master bond0
    bond-primary <eth_name_1> <eth_name_2>

    auto bond0
    iface bond0 inet static
    bond-slaves <eth_name_1> <eth_name_2>
    bond-miimon 100
    bond-mode 802.3ad
    bond-downdelay 100
    bond-updelay 100
    bond-xmit-hash-policy layer2+3
    address <ip_address>
    netmask <mask>
    gateway <gateway>
    dns-nameservers <dns_servers>


    • <eth_name_1>, <eth_name_2> is the network interface that is included in the aggregation;
    • <ip_address> is the IP address to use on the aggregated interface;
    • <mask> is the subnet mask;
    • <gateway> is a gateway;
    • <dns_servers> — DNS server address. We recommend using Selectel DNS:,
  9. Bring up the bond0 network interface:

    ifup bond0
  10. Restart the network services:

    /etc/init.d/networking start
  11. Verify that the bond0 network interface is assembled correctly:

    cat /proc/net/bonding/bond0